Creamy Mocha Frosting
["3/4 c. butter or margarine", "6 c. sifted powdered sugar", "1 Tbsp. cocoa", "1 egg yolk, beaten", "1/4 c. plus 1 1/2 tsp. cold brewed coffee"]
["Cream butter.", "Combine sugar and cocoa and gradually add to butter, beating until smooth.", "Add remaining ingredients, beat until light and fluffy.", "Spread between layers and on top and sides of cake.", "Garnish with chocolate leaves, if desired."]
["butter", "powdered sugar", "cocoa", "egg yolk", "cold brewed coffee"]