1. Place oven rack in lowest position. Heat oven to 375°F.
2. Prepare cake batter as directed on package. Transfer 4 cups batter to medium bowl; gradually fold in cocoa until well blended, being careful not to deflate batter. Alternately pour vanilla and chocolate batters into ungreased 10-inch tube pan. With knife or metal spatula, cut through batters for marble effect.
3. Bake 30 to 35 minutes or until top crust is firm and looks very dry. Do not underbake. Invert pan on heatproof funnel or bottle; cool completely, at least 1-1/2 hours. Carefully run knife along side of pan to loosen cake; remove from pan. Place on serving plate; drizzle with Chocolate Glaze. Let stand until set. Store, covered, at room temperature.
Combine 1/3 cup sugar and 1/4 cup water in small saucepan. Cook over medium heat, stirring constantly, until mixture comes to a boil. Stir until sugar dissolves; remove from heat. Immediately add 1 cup HERSHEY'®S Mini Chips® Semi-Sweet Chocolate; stir until chips are melted and mixture is smooth. Cool to desired consistency; use immediately. About 1 cup glaze