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Sweet, juicy plum harmonizes with buttery brown sugar oats in these crumble topped dessert bars.
Summertime at the farmers market or grocery store usually entails me loading up on things like tomatoes, zucchini, peaches, cherries, and corn. Plums are there too, but it’s rare that I give them a second glance. Which of course is absolutely ridiculous because plums are delicious!
In an effort to mend my ways, I recently bought an obscene amount of plums. They were too many to eat out-of-hand. Not sure what to make with them, I knew I wanted to keep it simple and let the natural sweet, tart plum flavor shine. Plum bars were the perfect choice.
With a jammy pie-like filling and brown sugar-sweetened, buttery, crumbly oat topping, you get the best of all worlds. Part plum pie, part plum crisp or crumble, part cookie bar, in portable dessert form that’s perfect for picnics, potlucks, or neighborhood barbecues where you promised to bring dessert and want to make something just a little unexpected.
What Makes This Recipe Special
- The jammy plum filling. It tastes like perfectly sweet, slightly tart ripe plum, but better. The other ingredients add subtle nuances to the flavor profile while letting the plums shine. Fresh thyme and cardamom are unique additions, but they’re completely optional.
- A crumbly streusel topping serves double duty as the base for these bars. We keep it simple with butter, brown sugar, nutty oats, and just a couple other things.
- It celebrates a lesser-celebrated fruit that deserves a chance to shine! Plums are underutilized (at least in my kitchen), and this recipe is a lovely way to enjoy them. It’s a real crowder-pleaser dessert, making it a good option for summer gatherings.
Ingredients
Breaking It Down
Ingredients Explained
In this section I explain the ingredients and give substitution ideas where applicable. For the full recipe (including the ingredient amounts), see the recipe card below.
Jammy Plum Filling Ingredients
- Fresh ripe plums – You can use any kind of plums you fancy (I used a mix of purple and red), just make sure they’re ripe for the most intense flavor.
- Sugar – Use granulated white sugar here. We’re essentially making plum pie filling for these bars; sugar adds sweetness and also helps thicken it.
- Salt – Enhances the flavor of plums.
- Fresh lemon juice – Adds bright, fresh flavor and increases the pectin, which helps the filling set (like when making jam).
- Fresh thyme – Thyme is the oddball addition to this recipe. It adds an herbaceous note with citrusy brightness and spicy undertones. With the small amount that we use in this recipe, you won’t necessarily be able to pull out the flavor of thyme, but you’ll notice it has an ingredient that you can’t quite put your finger on.
- Ground nutmeg, green cardamom, and allspice – Instead of going for a classic pie spice mixture with cinnamon, here with switch things up a little with nutmeg, green cardamom, and allspice. Nutmeg contributes warm, woody, and citrusy notes. Green cardamom also adds citrusy brightness, but a unique herby, piney-ness along with it. Allspice is one of my favorite spices to pair with plums; it adds sweet, warm spicy flavor notes of cinnamon, nutmeg, and cloves, as well as citrusy, peppery hints.
- Pure vanilla extract – For underlying flavor and aroma.
- Cornstarch – For the filling, we mix the cornstarch with cold water to form a slurry to help thicken it.
Top Crumble and Bottom Crust Ingredients
- Unsalted butter – Adds rich flavor and helps this crisp and brown. Make sure the butter is at room temperature.
- Light brown sugar – Buttery brown sugar oat topping that’s laced with vanilla makes these bars smell amazing as they bake.
- Pure vanilla extract – For flavor and aroma.
- Flour – The base of our bottom crust and top crumble is half all-purpose flour and half oats.
- Oats – Use old-fashioned rolled oats here for best results.
- Cornstarch – Lightens up the dough just a bit for the perfect texture.
- Salt – It pulls out the rich flavor of buttery and the nuttiness of oats.
Step-by-Step Instructions
1: Make the Plum Filling
- Wash and chop the plums.
- Add the plums, sugar, and salt in a medium saucepan over medium heat.
- Stir to coat the plums in sugar.
- Cover the saucepan and cook 10 minutes, stirring occasionally. After 10 minutes, turn the heat down to medium-low, lightly mash the plums with a potato masher (we still want some larger pieces), and cook uncovered 5 minutes, stirring frequently.
- Stir in the lemon juice, nutmeg, cardamom, allspice, vanilla, and cornstarch slurry. Cook until the mixture thickens, about 3 minutes, stirring constantly.
- Set aside to cool to room temperature, about 2 hours. (It will thicken during this time.)
2: Make the Top Crumble and Bottom Crust (It’s the Same Dough)
- Add the butter, brown sugar, and vanilla to a large bowl.
- Use a handheld electric mixer to beat until smooth and creamy.
- Add the flour, oats, cornstarch, and salt.
- Beat just until combined. (The mixture will look like large, moist crumbles.)
3: Assemble and Bake
- Press about half of the dough evenly into the bottom of the prepared pan.
- Spread the room temperature plum filling (see the Notes in the recipe card below for how much to use) evenly onto the dough.
- Crumble the remaining dough on top of the plum filling. Sprinkle 1 tablespoon oats on top.
- Bake until the top is golden brown and the filling is bubbling, about 50 minutes. Cool completely before slicing.
4: Cool and Finish with Powdered Sugar
Dust the top with powdered sugar (if desired), and serve.
Storage
- Fruit filling – Cool to room temperature, and then can store it in an airtight container in the fridge for up to 10 days or in the freezer for up to 6 months.
- Bar cookies – Cool to room temperature, and then store them in an airtight container at room temperature for up to 3 days, in the fridge for up to 1 week, or in the freezer for up to 3 months.
Pro Tips For the Best Plum Bars
- If you want to simplify the flavor here, omit the thyme, nutmeg, green cardamom, and allspice and add 1 teaspoon ground cinnamon instead.
- This recipe makes about 2 cups of plum filling. I use all of it in these bars, which are super jammy and reminiscent of pie slices (they’re easier to eat with a fork!). If you’re making these bars to take somewhere and want them less messy, only use about 1 cup of filling and freeze the rest of it.
Frequently Asked Questions
For this recipe, there’s no need to peel the plums. We chop them up, cook them down into a jammy consistency, and then bake them in cookie bars.
Yes. Here we cook the plums (essentially making plum pie filling), to thicken it before baking the bars. But don’t worry, it’s a very easy process. Make a double batch of filling and stash it in the freezer for up to 6 months so you can easily make this again anytime.
Yes. Letting the filling cool serves two main purposes. First, it allows the jammy filling to fully thicken and set. Additionally, it makes sure the hot filling doesn’t melt the butter in the crust, which can lead to a soggy crust on the bottom.
More Easy Recipes Using Summer Fruit
- Cherry Crisp Recipe with Fresh Cherries
- Peach Granola Recipe with Fresh Peaches
- Blueberry Pie Recipe with Frozen Blueberries
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Plum Bars Recipe with Crumble Topping
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Equipment
Ingredients
Plum Filling:
- 3 cups chopped fresh ripe plums use purple or red plums; no need to peel them; this is about 1 1/4 to 1/2 pounds or 6 large-ish plums
- 1 1/2 cups granulated white sugar
- 1/4 teaspoon salt
- 1 tablespoon fresh lemon juice
- 1/2 teaspoon minced fresh thyme
- 1/4 teaspoon ground nutmeg
- 1/4 teaspoon ground green cardamom
- 1/8 teaspoon ground allspice
- 1 teaspoon pure vanilla extract
- 3 1/2 tablespoons cornstarch mixed with 4 tablespoons cold water to form a slurry
Top and Bottom Crust:
- 1 cup unsalted butter at room temperature
- 2/3 cup light brown sugar lightly packed
- 2 teaspoons pure vanilla extract
- 1 1/2 cups all-purpose flour
- 1 1/2 cups old-fashioned rolled oats plus 1 tablespoon more for sprinkling on top if desired
- 2 tablespoons cornstarch
- 1/2 teaspoon salt
Other:
- 1 tablespoon powdered sugar for dusting on top (optional)
Instructions
Plum Filling:
- Cook. Stir together the plums, sugar, and salt in a medium saucepan over medium heat. Cover the saucepan and cook 10 minutes, stirring occasionally. After 10 minutes, turn the heat down to medium-low, lightly mash the plums with a potato masher (we still want some larger pieces), and cook uncovered 5 minutes, stirring frequently. Stir in the lemon juice, nutmeg, cardamom, allspice, vanilla, and cornstarch slurry. Cook until the mixture thickens, about 3 minutes, stirring constantly.
- Cool. Set aside to cool to room temperature, about 2 hours.
Top and Bottom Crust:
- Use a hand-held electric mixer to cream together the butter, brown sugar, and vanilla in a large bowl. Add the flour, oats, cornstarch, and salt, and beat just until combined.
Assemble and Bake:
- Prep. Preheat the oven to 350F. Line an 8 by 8-inch pan (or equivalent) with 2 pieces of parchment paper so it hangs over all 4 sides.
- Assemble. Press about half of the dough evenly into the bottom of the prepared pan. Spread the room temperature plum filling (see Notes below for how much to use) evenly onto the dough. Crumble the remaining dough on top of the plum filling. Sprinkle 1 tablespoon oats on top.
- Bake and cool. Bake until the top is golden brown and the filling is bubbling, about 50 minutes. Cool completely before slicing. Dust the top with powdered sugar (if desired), and serve.
Notes
- Plum Filling: This makes about 2 cups of filling. I use all of it in these bars, which are super jammy and reminiscent of pie slices (they’re easier to eat with a fork!). If you’re making these bars to take somewhere and want them less messy, only use about 1 cup of filling and freeze the rest of it.
- For a More Classic, Simpler Flavor Profile: Omit the thyme, nutmeg, green cardamom, and allspice and add 1 teaspoon ground cinnamon instead.
- Storage: Once the filling is cooled to room temperature, you can store it in an airtight container in the fridge for up to 10 days or in the freezer for up to 6 months. Once the jam cookie bars are cooled to room temperature, you can store them in an airtight container at room temperature for up to 3 days, in the fridge for up to 1 week, or in the freezer for up to 3 months.
Nutrition
Nutritional information is automatically calculated and should be used as an approximate.
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I’m the writer, recipe developer, photographer, and food stylist behind this blog. I love finding the human connection through something we all do every day: eat! Food is a common ground that we can all relate to, and our tables tell a story. It’s my goal to inspire you to get in the kitchen, try something new, and find a favorite you didn’t know you had.
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