Preheat oven 350. Grease jellyroll pan. Prepare cake as directed. Spread in jellyroll pan evenly. Bake 15-20 minutes. Cool 10 minutes. Remove from pan and cool completely on wire rack. Cut into 3 equal sections (loaf size).
Prepare frosting: Mix instant coffee with 2 tsp. hot tap water, stir in vanilla. Beat 1-1/2 sticks of margarine and cream cheese until blended. Add powdered sugar, beat until fluffy. Mix in coffee mixture. Layer cake with frosting. Refrigerate until firm and cold, about 1 hour.
Prepare glaze: Over low heat in 1-qt saucepan, melt chocolate chips, 1 stick of margarine, and corn syrup. Pour glaze over firm cake, allowing to run down sides. Refrigerate until set, at least 15 minutes.