Preheat oven to 425F. Spray 12 cups of a muffin pan with non-stick cooking spray or line with paper muffin cups; set aside
In a medium mixing bowl, whisk together the flour, baking powder, baking soda, cinnamon, and salt; set aside
In a large mixing bowl, beat together the butter, brown sugar, and granulated sugar with an electric mixer on medium speed until smooth
Add the eggs, sour cream, milk, and vanilla extract and mix until well combined
Pour the dry mixture into the wet mixture and stir together just until the dry ingredients are incorporated
Fold in the chopped apples
Scoop the batter into the cups of the prepared muffin pan, filling each to the top
Spoon the crumb topping evenly over all of the muffins.
Bake the muffins at 425F for 5 minutes, then reduce the oven temperature to 350F and bake for an additional 15-18 minutes until a toothpick inserted into the center comes out clean-DO NOT REMOVE THE MUFFINS FROM THE OVEN WHEN YOU CHANGE THE TEMPERATURE just reset it and keep baking
Remove the muffins from the oven and cool in the pan for 5 minutes, then remove and cool completely on a wire cooling rack