Don't miss this decadence: sour cream, crushed Oreos, melted candy bars — swwweeeet!
Preheat oven to 350 degrees. Line bottoms of two round 9-by-9-inch baking pans with parchment paper and spray pans with baking spray with flour.
Prepare cake mix according to directions on box then add the sour cream. Fold in the 16 crushed Oreos and stir until evenly combined. Divide batter between the prepared cake pans and bake according to directions on box (or until toothpick comes out clean). Let cool completely.
To make the frosting: Beat butter until light and fluffy. Add the melted candy bars. Gradually mix in the powdered sugar alternately with milk. Add vanilla and beat until smooth.
Place cooled cake layer on plate and spread with frosting. Sprinkle half of the 10 crushed Oreos on top of the frosting. Add second layer of cake and frost entire top and sides.
Top with crushed Oreos. Optional: garnish with mini Oreos around sides of cake and on top.