In large bowl, beat butter or margarine untill light and fluffy. Gradually beat in sugar, then eggs and vanilla. Combine flour cocoa, cornstarch, instant coffe, baking soda and salt beat in alternately with milk begining and ending with flour mixture. Grease two 9" rounds and lightly dust with cocoa; pour batter into prepared pans. Bake in preheated oven for 20 minutes; cool in pans on wire rack for 10 minutes. Remove from pans; cool the rest of the way. Take a long sharp knife and cut each cake in 2 layers; spread filling over the 2 bottom halves. Place on tops; cover with wrap till you serve. FILLING: Beat together all ingredients then refridgerate till needed. ----