Heat oven to 350°F. Grease 12-cup fluted tube cake pan with 1 tablespoon butter. Cut all 13 biscuits into quarters; set aside.
In large microwavable bowl, place marshmallows, 1/2 cup butter, hot fudge topping and vanilla. Microwave uncovered on High 1 to 2 minutes, stirring once, until melted. Using wire whisk, stir until smooth.
In medium bowl, stir sugar and cocoa until blended.
Carefully place 1/4 of the biscuit pieces into hot chocolate mixture, gently folding in to coat. Add another 1/4 of the biscuits, gently folding in to coat. Using tongs, remove biscuits from chocolate, letting excess chocolate drip off. Drop 1 biscuit piece at a time into sugar mixture; spoon sugar over biscuit to coat. Layer biscuits in cake pan. Repeat with remaining biscuits. Sprinkle any remaining sugar mixture over biscuits.
Bake 30 to 40 minutes or until biscuits are deep golden and no longer doughy in center. Cool in pan 5 minutes. Place heatproof serving plate upside down over pan; carefully turn plate and pan over. Remove pan; immediately scrape any remaining topping in pan onto bread. Pull apart warm bread to serve.