Line a muffin tin with paper liners. Preheat the oven to 375 degrees.
Combine melted butter, sugars, eggs, vanilla, sour cream and milk in a bowl until mixed. Mix together flour, baking powder, baking soda, cinnamon and salt.
Add the dry ingredients into the wet ingredients, mixing until just combined. Fold in the shredded apples until just incorporated throughout the batter. The batter will be thick and be sure not to overmix.
Scoop the batter into the lined muffin tray until about ¾ full. Sprinkle about a tablespoon of crumble topping on top of each muffin.
Bake for about 20 minutes or until a cake tester or toothpick comes out clean or with a few moist crumbs. Cool for 10 minutes in the muffin tin.