Oatmeal Cream Pies with Rum-Raisin Brown Sugar Buttercream Frosting

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Was anyone else a fan of the cream-filled oatmeal cookie sandwiches as a kid?

They were a very rare treat for my sister and I since they weren’t something my mom ever bought, which made them all the more fun to eat at our friends’ houses when mom wasn’t around.

Those iconic treats were the inspiration for these cookies, and while I would love to tell you that these cookies were given a healthy makeover, the fact of the matter is that just about the only healthy thing about these cookies is that they contain oatmeal (and eggs, lol!). However, at least by making them at home instead of buying them premade, you know the quality of ingredients that’s going into them, and of course there are no preservatives or other ingredients you can’t pronounce.

Plus, the homemade variety is so much more delicious, and especially this fun flavor profile. Instead of making a plain white cream filling, I made a Rum-Raisin Brown Sugar Buttercream Frosting. Because why not, right?


I’ve experimented with several brown sugar buttercreams throughout the years, and the method that I came up with and shared below is the easiest and every bit as delicious as other versions. Instead of making a Swiss or Italian meringue buttercream, I wanted to stick with an American buttercream, which is by far the fastest to make. However, the issue is that brown sugar can create a grainy texture in frosting, so it has to be treated with a bit of care. Instead of dealing with brown sugar directly, I remembered that brown sugar is nothing more than white sugar with molasses added back in. Because of this, I decided to go a much easier route with the frosting: just use powdered sugar (which is what is normally used in American buttercream) and add molasses (which is a liquid and won’t cause graininess). It worked like a charm and the frosting came out perfectly.


The flavor of the frosting is fabulous. The molasses cuts through a bit of the super sweetness that buttercream normally has, and adds depth and complexity. I chose to flavor the brown sugar buttercream with rum flavoring and golden raisins, but this recipe can easily be adjusted to make whatever brown sugar buttercream flavor you like:

Brown Sugar Buttercream: Omit the butter flavor, rum flavor, and raisins. Add up to 1 teaspoon more milk if needed.

Brown Sugar-Cinnamon Buttercream: Omit the butter flavor, rum flavor, and raisins. Add 1/2 teaspoon ground cinnamon, and up to 1 teaspoon more milk if needed.

Brown Sugar-Maple Buttercream: Omit the butter flavor, rum flavor, and raisins. Add 1 teaspoon maple flavor.

I think this frosting would be lovely on any number of cakes, like gingerbread, classic vanilla cake, or even banana bread if you want to add a bit of decadence.

And it’s absolutely perfect in these classic cookies.


Oatmeal Cream Pies with Rum-Raisin Brown Sugar Buttercream Frosting

Prep Time: 25 minutes

Cook Time: 25 minutes

Yield: Yields 24 cookie sandwiches, or 48 cookies and about 1 1/2 cups frosting

Oatmeal Cream Pies with Rum-Raisin Brown Sugar Buttercream Frosting


    Oatmeal Cookies:
  • 1 cup (230 g) unsalted butter, at room temperature
  • 1 cup (230 g) dark brown sugar, packed
  • 1 1/2 teaspoons pure vanilla extract
  • 2 large eggs
  • 1 1/2 cups + 2 tablespoons (210 g) all-purpose flour
  • 3/4 teaspoon baking soda
  • 1/2 teaspoon salt
  • 1/4 teaspoon cinnamon
  • 1 1/2 cups (150 g) quick-cooking rolled oats
  • Rum-Raisin Brown Sugar Buttercream Frosting:
  • 5 tablespoons (70 g) unsalted butter, at room temperature
  • 5 tablespoons (60 g) unflavored vegetable shortening, at room temperature
  • 2 teaspoons blackstrap molasses
  • 1/2 teaspoon pure vanilla extract
  • 1/2 teaspoon butter flavor
  • 1/2 teaspoon rum flavor
  • 2 cups (240 g) powdered sugar
  • 1 tablespoon milk (more or less as needed)
  • 2 tablespoons golden raisins (sultanas), finely chopped


  1. Preheat oven to 350F; line 2 large baking sheets with parchment paper.
  2. For the cookies, cream together the butter and brown sugar in a large bowl, and then cream in the vanilla and eggs.
  3. Sift the flour, baking soda, salt, and cinnamon into the bowl with the wet ingredients, and stir to combine. Stir in the oats.
  4. Drop the dough by the tablespoon onto the prepared baking sheets (I like to use a 1-tablespoon ice cream scoop), leaving about 2 to 3 inches between the cookies so they have room to spread out. (You should get about 48 cookies, so you will need to cook them in batches.)
  5. Bake until the cookies are set on the bottom but look just a touch doughy in the center, about 7 to 8 minutes.
  6. Let the cookies cool for 10 minutes on the baking sheets, and then transfer them to a wire rack to finish cooling. Cool the cookies completely before sandwiching them with the frosting.
  7. For the frosting, use an electric beater to mix together the butter, shortening, molasses, vanilla extract, butter flavor, and rum flavor in a large bowl until smooth. Gradually beat in the powdered sugar, slowly adding enough milk so the frosting reaches your desired consistency. Once smooth, stir in the raisins. Store the frosting in an airtight container in the fridge until ready to use (it will keep for up to a week in the fridge), then let it come to room temperature and beat it again before using.
  8. Assemble the pies by sandwiching two cookies together with frosting in the middle.

Update (November 3, 2013): I made this dish again and perfected the recipe so I updated this post.

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Hello! I’m Faith and I write An Edible Mosaic. This is my recipe collection of international favorites and updated American classics, with an emphasis on seasonal dishes. I focus on real foods that sustain body and mind, bring people together, and make a house a home. Welcome to my mosaic of recipes.

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