PREHEAT oven to 350°F. Beat cake mix, dry pudding mix, eggs, sour cream, oil, 1/2 cup of the water and 1/2 cup of the flavored instant coffee in large bowl with electric mixer on low speed just until moistened, stopping frequently to scrape side of bowl. Beat on medium speed 2 min. or until well blended. Chop 4 squares of the chocolate; stir into batter. Pour evenly into 2 greased and floured 9-inch round cake pans.

BAKE 40 to 45 min. or until toothpick inserted in centers comes out clean. Cool in pans 15 min.; remove from pans. Cool completely on wire racks.

STIR remaining 1/4 cup flavored instant coffee into whipped topping. Place 1 cake layer on serving plate; spread with the whipped topping mixture. Top with second cake layer. Microwave remaining 4 squares of chocolate, the butter, corn syrup and remaining 1 Tbsp. water in medium microwaveable bowl on HIGH 1-1/2 min.; stir until chocolate is completely melted. Spread glaze over top of cake, allowing glaze to drip down side of cake. Serve immediately or refrigerate until ready to serve.