Preheat oven to 350°F (175°C). Grease and line two 9-inch cake pans with parchment paper.
In a large bowl, whisk together flour, sugar, cocoa powder, baking powder, baking soda, and salt.
Add buttermilk, vegetable oil, eggs, and vanilla extract. Mix until well combined.
Stir in hot coffee until the batter is smooth. The batter will be thin.
Fold in crushed Oreo cookies.
Divide the batter evenly between the prepared pans. Bake for 30-35 minutes or until a toothpick inserted in the center comes out clean.
Let cakes cool in pans for 10 minutes, then transfer to a wire rack to cool completely.
To make the frosting, beat the softened butter until creamy.
Gradually add powdered sugar, alternating with heavy cream, and beat until fluffy.
Stir in vanilla and finely crushed Oreos until well mixed.
Place one cake layer on a serving plate and spread frosting on top.
Add the second cake layer and frost the entire cake.
Decorate with whole Oreos around the edges and sprinkle with crushed Oreos on top.
Refrigerate for 30 minutes before slicing for cleaner cuts.