Preheat oven to 350°F. Butter and flour 3 (8) inch round cake pans or spray with baking spray. Set aside.
In a medium size mixing bowl, use an electric mixer to cream together butter, granulated sugar, brown sugar and vanilla. Cream for 2-3 minutes until combined. Add the eggs 1 at a time beating well after each addition.
In a separate bowl, use a whisk to sift together flour, cocoa, baking powder, baking soda, espresso powder and salt. Add to the creamed mixture alternately with the buttermilk beginning and ending with flour.
After all of the dry ingredients have been added, stop and scrape the sides and bottom of the bowl. Beat the batter for 30 seconds on medium-high just until creamy. Divide evenly between the pans.
Bake for 22-25 minutes or until a toothpick inserted into the center comes back clean. Cool in the pans on a cooling rack just until warm to the touch. Remove from the pan and cool completely.
To make Chocolate Sour Cream Frosting: In a medium size saucepan over low medium-low heat, melt together butter and cocoa. Once smooth, remove from heat and scrape into a mixing bowl.
Use an electric mixer fitted with the whisk attachment, to gradually add powdered sugar alternately with sour cream. Beat on medium speed until smooth. Test spreading consistency then add milk or cream 1 tablespoon at time to thin further, if needed.
Place cooled layers on a cake stand or platter covered with strips of wax paper. Frost between layers, top and sides of cake. Decorate with sprinkles, if desired.
Store chilled in an airtight container.