Preheat the oven to 350°F (175°C).
Grease and flour two 9-inch round cake pans.
In a large mixing bowl, combine flour, cocoa powder, baking powder, baking soda, sugar, and salt.
Add eggs, milk, vegetable oil, and vanilla extract to the dry ingredients.
Fold in the crushed Oreo cookies gently.
Divide the batter evenly between the prepared pans.
Bake for 30–35 minutes or until a toothpick inserted comes out clean.
Remove cakes from the oven and let them cool in the pans for 10 minutes.
Transfer to a wire rack to cool completely.
Prepare the frosting by creaming softened butter until light and fluffy.
Gradually add powdered sugar and beat until smooth.
Add heavy cream to the frosting and mix until combined.
Once the cakes are cool, spread frosting between the layers and on top and sides of the cake.
Decorate the top with mini Oreos and crushed Oreos.