HEAT oven to 350°F.
BEAT cake mix, dry pudding mix, eggs, sour cream, oil and 1/2 cup each flavored instant coffee and water in large bowl with mixer on low speed just until moistened, stopping frequently to scrape bottom and side of bowl. Beat on medium speed 2 min. or until well blended. Chop 4 oz. chocolate; stir into batter. Pour into 2 greased and floured 9-inch round pans.
BAKE 40 to 45 min. or until toothpick inserted in centers comes out clean. Cool in pans 10 min. Remove from pans to wire racks; cool completely.
STIR remaining 1/4 cup flavored instant coffee into COOL WHIP. Stack cake layers on plate, spreading COOL WHIP mixture between layers. Microwave butter, corn syrup and remaining chocolate and water in medium microwaveable bowl on HIGH 1-1/2 min.; stir until chocolate is completely melted. Spread over top of cake, allowing glaze to drip down side.