For the crust:
- 1 1/2 cups all-purpose flour
- 1 cup whole wheat flour
- 1 tablespoon granulated sugar
- 1 teaspoon salt
- 2 sticks chilled unsalted butter, cut into small cubes
- 1/2 cup ice-cold water
For the oatmeal cookie topping:
- 3/4 cup old-fashioned rolled oats
- 6 tablespoons brown sugar
- 2 tablespoons all-purpose flour
- 1/4 teaspoon cinnamon
- Pinch salt
- 3 tablespoons chilled unsalted butter, cut into small cubes
For the apple filling:
- 1/4 cup granulated sugar
- 2 tablespoons brown sugar
- 1 tablespoon all-purpose flour
- Pinch nutmeg
- 1 1/2 teaspoons lemon juice
- 1 1/2 lbs sweet-tart apples (I used Pink Lady, but Honeycrisp or even Gala would work well), peeled, cored and thinly sliced
For the icing:
- 1 cup powdered sugar
- 2 to 3 tablespoons milk
- 1/2 teaspoon vanilla
- To make the pie dough: Combine flours, sugar and salt in a large bowl. Add butter cubes and, using a pastry blender or your fingers, cut in the butter until the mixture resembles coarse crumbs.
- If the butter has softened too much, place the bowl in the freezer for 5 minutes. Pour ice-cold water into mixture in bowl; stir with a spatula until a rough dough forms.
- Turn dough out onto a countertop and knead a few times until dough comes together; divide in half and shape each half into a ball. Flatten each ball into a 1-inch thick disc. Cover tightly with plastic wrap and chill in fridge 1 hour.
- Meanwhile, make the oatmeal cookie topping: In a large bowl (you can use the bowl you just used to make the pie dough to cut down on dishes), combine oats, brown sugar, flour, cinnamon and salt. Cut in butter with fingers and mix until well combined. Chill mixture until pie dough is fully chilled and ready to bake.
- To make the apple filling: In a large bowl, combine sugars, flour, nutmeg and lemon juice. Add apple slices and toss until well combined.
- Heat oven to 375 degrees F. When pie dough is fully chilled, sprinkle a countertop generously with flour, then roll out each pie dough disc to a rough 1/8-inch thickness. Use a 4-inch round biscuit or cookie cutter to cut out dough rounds; re-roll scraps one time to cut out more rounds (you should end up with about 18 rounds). Press each round into the bottom and sides of an ungreased muffin cup.
- Divide apple filling among muffin cups (the filling will be a bit mounded, but it’ll bake down). Sprinkle tops evenly with oatmeal cookie topping. Bake 40 minutes until topping is golden brown and pie crust is baked through.
- Cool mini pies in muffin cups 30 minutes, then use a butter knife or spatula to carefully transfer pies to a cooling rack to cool completely.
- Combine all icing ingredients in a small bowl, adding more milk or powdered sugar as needed until a thick but pourable icing forms. Drizzle icing over fully cooled pies.