Dutch Apple Pie Cookies

All-Butter Pie Dough:

1. Mix vinegar and water together, then add a few ice cubes. Store in fridge until ready to use.
2. In a large bowl, whisk together flour, vanilla sugar, and salt.
3. Add cold, cubed butter to flour mixture, tossing around gently to coat. With pastry blender in one hand, cut in butter while rotating bowl in quarter-turns with your other hand. Stop once the pieces of butter are roughly pea sized. (You’ll want to have some that are a little bigger and some that are a little smaller to maximize the delicious flakiness!)
4. Add ice cold water-vinegar mixture one tablespoon at a time, quickly mixing together with your hands. Continue adding water one tablespoon at a time until the dough comes together. The goal is for the dough to hold together when squeezed into a ball, but with a few dry bits still left in the bowl.
   NOTE: Do NOT add all of the water at once. You don’t want the dough to get so wet that it becomes sticky. You should only be adding 4–5 tablespoons of water total.
5. Wrap dough in cling film, then press into a patty shape about 1-inch thick. Place wrapped dough in fridge overnight. (You could refrigerate for only two hours if you’re in a hurry, but overnight is recommended.)

Apple Filling:

1. In a large pot, mix together all filling ingredients until apples are coated with sugar, cinnamon, and cornstarch.
2. Stirring occasionally, cook over medium heat until apples have softened and liquids have thickened, about 12 minutes.
3. Pour apple filling into a large bowl or spread onto a rimmed baking sheet. Allow to cool somewhat.

Streusel Topping:

1. In a large bowl, whisk together flour, brown sugar, oats, cinnamon, and salt.
2. With your hands, work the butter into the dry ingredients until the mixture looks like wet sand.

Assembly & Baking:

1. When you’re ready to create your pie cookies, flour your work surface and rolling pin. Retrieve dough from fridge, place on your well-floured surface, and sprinkle top with a little bit of flour.
2. Begin gently rolling out the dough into a circle, making sure to pick up and rotate the dough every few rolls.
3. Once your dough is roughly a 12–14" circle and ¹/₈- to ¼-inch thick, cut dough into circles using a cookie or biscuit cutter. (We used a 2.5" biscuit cutter.)
4. Lightly grease the wells of 2 muffin tins. Place one dough circle into the bottom of each well, gently pressing the excess into the bottom corners and up the sides a tiny bit. Place muffin tins into fridge for at least 15 minutes.
5. Heat oven to 350°F.
6. Once dough has chilled, par-bake crust bottoms for 8 minutes.
7. Place muffin tins on wire rack and allow to cool for 10 minutes.
8. Now it’s assembly time! Spoon 1 tablespoon of apple filling on top of each bottom crust.
9. Sprinkle a heaping teaspoon of streusel on top, gently pressing into filling.
10. Dust each pie cookie with ¼ to ½ teaspoon of vanilla sugar.
11. Bake until lightly browned, about 25 minutes.
12. Allow pie cookies to cool in pans for at least 15 minutes.