Step 1: Preheat your oven to 350°F (175°C) and grease two 8-inch round cake pans, lining the bottoms with parchment paper.
Step 2: In a large bowl, whisk together the flour, sugar, cocoa powder, baking soda, baking powder, and salt.
Step 3: Add the buttermilk, oil, eggs, and vanilla extract to the dry ingredients and mix on medium speed until well combined.
Step 4: Reduce speed to low and carefully pour in the boiling water. Stir by hand until the batter is smooth (it will be thin).
Step 5: Divide the batter evenly between the prepared pans and bake for 30-35 minutes, or until a toothpick comes out clean.
Step 6: Allow cakes to cool in pans for 10 minutes, then transfer to a wire rack to cool completely.
Step 7: For the frosting, beat the softened butter until creamy. Gradually add powdered sugar, heavy cream, and vanilla, beating until fluffy. Fold in the crushed Oreos.
Step 8: Assemble the cake by placing one layer on a plate, topping with frosting, then adding the second layer. Frost the exterior and decorate with whole Oreos.