Preheat oven to 350°F (175°C) and line a cupcake pan with 12 cupcake liners. Mix the dry ingredients in a bowl.

Cream together sugar, unsalted butter, and vegetable oil until light and fluffy, then add egg, sour cream, and vanilla.

Gradually incorporate dry ingredients with room temperature milk until combined, then fill cupcake liners and bake for 20 minutes.

Let the cupcakes cool completely.

Whip room temperature unsalted butter until light and fluffy, then gradually add powdered sugar, vanilla, cinnamon, and salt.

Slowly incorporate heavy cream until smooth and spreadable.

Combine diced apples, sugar, water, lemon juice, and cinnamon in a saucepan, cooking until apples soften.

Create a cornstarch slurry and add to mixture, cooking until thickened, then cool to room temperature.

Mix flour, brown sugar, and cinnamon, then cut in butter until resembling coarse crumbs.

Bake at 350°F (175°C) for 10-15 minutes, then let cool completely.

Pipe frosting onto each cooled cupcake, add apple filling on top, then sprinkle crumble topping.