In a large mixing bowl, whisk together 1 cup of all-purpose flour, 1/2 cup of light brown sugar, 1 teaspoon of ground cinnamon, and 1/4 teaspoon of ground nutmeg. Cut in 1/2 cup of cold unsalted butter until the mixture resembles coarse crumbs. Refrigerate for 30 minutes.

Peel, core, and dice 2-3 apples. Combine with 1/4 cup of granulated sugar, 1 tablespoon of lemon juice, 1/2 teaspoon of ground cinnamon, and 1 tablespoon of all-purpose flour. Mix well and set aside.

Preheat your oven to 350°F and line a muffin tin with paper liners. In another bowl, whisk together 1.5 cups of all-purpose flour, 1 teaspoon of baking powder, 1/2 teaspoon of baking soda, and 1/4 teaspoon of salt. Cream 1/2 cup of softened unsalted butter and 1 cup of light brown sugar until fluffy. Add 2 eggs and 2 teaspoons of vanilla, mixing well.

Mix in the dry ingredients alternately with 1/2 cup of sour cream and 1/4 cup of milk, starting and ending with dry ingredients. Stir gently until just combined.

Spoon batter into muffin tin, filling halfway. Add apple filling, then top with crumble. Bake for 20-25 minutes until a toothpick comes out clean.

Cool in the tin for 5-10 minutes, then transfer to a wire rack. If desired, drizzle with caramel sauce and dust with powdered sugar.