Apple Slab Pie with Nutty Oat Crumble Topping has a sweet spiced apple filling with a hint of vanilla, an all-butter pastry crust, and a nutty oat crumble topping.
Toss together all ingredients in a large bowl until the apples are coated. Cover the bowl and let the mixture sit for 1 hour, stirring a couple times.
For the Crust:
Whisk together the flour, pulverized walnuts (if using), and salt in a large bowl and then cut in the butter with a pastry cutter or a fork until it looks like coarse meal. Add water 1 tablespoon at a time, working the dough together with your fingertips just until it comes together, and only adding enough water so the dough comes together when you squeeze it. Gather the dough together into a ball and then flatten it into a rectangle; wrap it in plastic wrap and refrigerate until chilled, about 30 minutes.
For the Crumble Topping:
Use a fork to mix the flour and brown sugar together in a large bowl. Cut in the butter, and then stir in the oats and walnuts.
To Assemble and Bake:
Preheat the oven to 375F; get out a 15 by 10 by 1-inch baking sheet. (I don’t bother lining the baking sheet because there’s enough butter in the crust to prevent it from sticking, but you can line the bottom with parchment paper if you want).
Roll out the dough to an 18 by 13-inch rectangle on a lightly floured surface. Drape it over the rolling pin to help you transfer the dough to the prepared baking sheet. If necessary, trim the dough to within ¾-inch of the edge of the pan, and then fold it over and flute it as desired. Use the tines of a fork to poke a few holes in the bottom of the crust.
Give the apple filling a good stir and spread it (along with any juices that have collected) into the prepared crust. Sprinkle on the crumble topping.
Bake the pie until the apples are tender and the crust is golden, about 40 to 45 minutes; cool on top of a wire rack.
For the Glaze:
Once the pie is cooled, whisk together all ingredients for the glaze and drizzle on top.
Let the glaze set before cutting and serving.
Notes
The best apples for this Apple Slab Pie are Granny Smith, Northern Spy, Jonagold, Braeburn, or Honeycrisp.
To store this after baking, cover it with plastic wrap and keep it at room temperature for up to 2 days. After that, store it covered in the fridge for up to 3 days more.
You can cut the pieces bigger or smaller depending on how many people you’re serving!