1. Heat oven to 375°F. Grease 13x9x2-inch baking pan.
2. Combine baking mix and cocoa; stir in 2 cups sweetened condensed milk, 1/2 cup syrup and vanilla until blended in large bowl. Spoon evenly into prepared pan; set aside.
3. Combine remaining sweetened condensed milk, remaining 1 cup syrup and hot water in small bowl. Pour liquid mixture carefully over top of mixture in pan; DO NOT STIR.
4. Bake 25 to 30 minutes or until center is set and cake begins to pull away from sides of pan. Let stand 15 minutes; spoon into dessert dishes, spooning pudding from bottom of pan over top. Serve warm; garnish with whipped topping, if desired. Cover; refrigerate leftover cake. 16 to 20 servings.
* One 16-oz. can HERSHEY'S Syrup contains 1-1/2 cups syrup.