For the crumb topping, combine the flour, sugar, cinnamon, and salt in a medium mixing bowl. Stir in the melted butter until just combined. Refrigerate until ready to use.

Preheat oven to 400°F (204°C). Line a 12-cup muffin tin with paper liners.

In a large mixing bowl, combine 3 cups all-purpose flour, baking powder, apple pie spice, and 1/2 teaspoon salt. Set aside.

In a stand mixer or large bowl, combine 1/2 cup unsalted butter and both sugars. Beat on medium-low speed until light and fluffy, about 3 minutes.

Add the eggs and yolk one at a time, beating well after each addition. Slowly beat in vanilla, buttermilk, and sour cream.

Reduce mixer speed to low and gradually add the dry ingredients, mixing until just combined. Do not over mix.

Turn off the mixer and gently fold in the chopped apples using a rubber spatula or wooden spoon.

Divide the batter evenly among the muffin cups. Crumble the topping on each muffin, piling it high in the center and gently pushing it into the batter.

Bake for 22 to 24 minutes, or until the tops are lightly golden brown and a toothpick inserted in the middle comes out clean.

Allow muffins to cool in the pan for 15 minutes, then transfer to a wire rack. Drizzle honey on top if desired, and serve warm.