For the Cake

1. Preheat oven to 350°F.
2. Grease cake pans with butter and line bottoms with parchment rounds. Butter the parchment and flour entire pan, dusting off excess.
3. Cream butter and sugars until light and fluffy (approx 3-4 min) on medium-high speed. Add eggs one at a time, then add vanilla. Mix well.
4. In a separate bowl, sift together dry ingredients (flour, cocoa, baking soda, salt). In another bowl, whisk together buttermilk, coffee and sour cream.
5. On low speed, add in alternating thirds beginning with buttermilk and ending with flour. Scrape down sides when necessary. Mix until just incorporated.
6. Bake for 20-25 minutes, until center is set.
7. Cool layers in the pans for 10 minutes, then remove cakes from pans.

For the Buttercream

1. On medium-high speed in a stand mixer, beat the butter and shortening until smooth (approx 4 min).
2. Slowly add the powdered sugar, scraping the sides when necessary.
3. Add the cream and vanilla and beat at medium speed until it reaches the consistency you like, adding more cream if you’d prefer.
4. Set aside 2 cups of plain buttercream. Now on low speed, combine the crushed Oreos into the frosting until they are mixed in thoroughly.
5. When the cake layers are completely cooled, cut each in half to make 4 layers. Layer the cake with the Oreo buttercream.