Preheat your oven to 350°F (175°C) and line a muffin tin with cupcake liners.

In a mixing bowl, combine flour, sugar, cocoa powder, baking powder, baking soda, and salt.

Add the egg, milk, vegetable oil, and vanilla extract to the dry ingredients and mix until smooth.

Fold in the crushed Oreo cookies.

Pour the batter into the prepared muffin tin, filling each liner about 2/3 full.

Bake for 18-20 minutes or until a toothpick inserted in the center comes out clean.

Allow the cupcakes to cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.

In a mixing bowl, beat the softened butter until creamy.

Gradually add the powdered sugar and mix until well combined.

Add the heavy cream and vanilla extract, then beat until the frosting is light and fluffy.

Fold in the crushed Oreo cookies.

Once the cupcakes are completely cool, use a spatula or piping bag to frost each cupcake with the Oreo frosting.

Sprinkle the tops with additional crushed Oreo cookies for decoration.