Chocolate mocha Cake

Preheat oven to 350 deg. Grease 15 1/2 x 10 1/2 jelly-roll pan; line bottom with waxed paper; grease and flour paper. Prepare cake mix as label directs. Spoon batter into jelly-roll pan, spreading evenly. Bake 15 to 20 minutes until toothpick inserted in center of cake comes out clean. Cool cake in pan on wire rack 10 minutes. Remove cake from pan; peel off and discard waxed paper. Cool cake completely on wire rack. In cup, mix instant coffee powder with 2 teaspoons hot water until coffee dissolves; stir in vanilla extract. Cut 3/4 cup butter into small pieces. In large bowl, with mixer at medium speed, beat cut-up butter and cream cheese just until mixed. Add powdered sugar, beat at low speed just until blended. Increase speed to high; beat until fluffy, scraping bowl often. Reduce speed to medium; gradually beat in coffee mixture, scraping bowl often, just until well combined. With serrated knife, cut cooled cake lengthwise into 3 equal pieces for cake layers. Place one cake layer on long platter; spread with 1/2 cup coffee butter cream. Top with second layer, then 1/2 cup coffee butter cream. Place remaining layer on top. Spoon about 1 cup butter cream into decorating bag with medium-size star tube; set aside. With metal spatula, spread sides and top of cake with remaining butter cream, making butter cream as smooth as possible. Refrigerate cake until coffee butter cream is firm and cold, about 1 hour. In heavy 1 quart saucepan over low heat, heat semisweet chocolate, corn syrup, and 1/2 cup butter until melted and smooth, stirring frequently. Let glaze cool 5 minutes. Tuck strips of waxed paper under cake to keep platter clean when glazing cake. Pour glaze along top of cake, allowing some glaze to drip down sides of cake. Refrigerate cake until glaze is set, about 15 minutes.