Preheat the oven to 425°F. Lightly spray a 12-cup muffin tin with non-stick spray, or line it with paper liners and set aside.

Make the crumb topping - in a small bowl, combine the sugar, brown sugar, flour, cinnamon and salt. Drizzle the melted butter over everything and stir until everything is combined and clumping together. Set aside.

In a large bowl, whisk together the flour, baking powder, salt and cinnamon. In another bowl, whisk together the sugar, eggs, melted butter and oil until well combined. Add the milk and vanilla and whisk until combined. Add this mixture to the flour mixture and stir until just combined.

Add the apples, folding in gently, until just combined.

Scoop the muffin batter into the prepared muffin tin, dividing it between the 12 muffin cups. They should be almost full. Top the muffins with crumb topping, dividing the mixture between the 12 muffin cups.

Bake for 17-20 minutes, or until a toothpick inserted in the center of a muffin comes out clean. Allow the muffins to cool for 5-10 minutes in the muffin tin, and then remove them to a wire rack to cool completely.

In a small bowl, whisk together the powdered sugar and milk until smooth to make the glaze. Drizzle the glaze over top of the cooled muffins.