Preheat your oven to 350°F (175°C) and line a cupcake pan with liners.
In a large bowl, whisk together flour, sugar, cocoa powder, baking powder, baking soda, and salt.
In another bowl, combine vegetable oil, eggs, vanilla extract, and buttermilk.
Mix the wet ingredients into the dry ingredients until just combined.
Fold in the crushed Oreo cookies gently.
Divide the batter evenly among the cupcake liners, filling them about 2/3 full.
Bake for 18-20 minutes, or until a toothpick inserted comes out clean.
Allow cupcakes to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
For the frosting, beat the softened butter until creamy, then gradually add powdered sugar.
Mix in heavy cream until you reach your desired consistency, then pipe onto the cooled cupcakes.