In a medium bowl, whisk together 1 cup flour, brown sugar, 1/2 teaspoon cinnamon, and 1/4 teaspoon nutmeg. Add the cold butter cubes and cut them in until you have coarse crumbs. Cover and refrigerate.

In a medium bowl, stir together the diced apples, 2 tablespoons granulated sugar, lemon juice, 1 teaspoon cinnamon, 1/4 teaspoon nutmeg, and 1 tablespoon flour until apples are lightly coated.

Preheat the oven to 350°F (175°C) and line a 12-cup muffin tin with cupcake liners.

In a medium bowl, whisk together 1 1/2 cups flour, baking powder, baking soda, and salt.

In a large bowl, cream the softened butter and 3/4 cup sugar for 3–5 minutes until fluffy.

Add eggs one at a time and mix well before adding the next.

In a small bowl, whisk sour cream (or yogurt) and milk until smooth.

Add the dry ingredients to the butter mixture alternating with the sour cream mixture, mixing just until combined.

Spoon about 2 tablespoons of batter into each liner, followed by 2 tablespoons of apple filling, and sprinkle generously with the chilled crumble topping.

Bake for 20–25 minutes until a toothpick comes out clean.

Cool in the tin for a few minutes before transferring to a wire rack. Drizzle with caramel sauce and/or dust with powdered sugar before serving.