Preheat the oven to 350 degrees and spray your pan (13X9) with non stick spray.
Mix the pudding mix, one package of hot cocoa mix, and milk in a bowl. Use a whisk.
Stir in the cake mix until moist. Fold in half of the marshmallows.
Put it into the cake pan and spread it out. Sprinkle on the chocolate chips.
Bake in the oven for 35 minutes.
Remove and add on the rest of the marshmallows asap. Let the cake cool for 1 hour.
Before serving add on the other hot cocoa mix envelope and some whipped cream!
Notes
Use hot water or hot milk for extra fudginess: Warm liquid helps bloom the cocoa in the cake mix and pudding mix, giving you a deeper chocolate flavor and a softer, molten texture.
Add a pinch of salt: Just 1–2 pinches enhances the chocolate flavor and balances the sweetness without making the cake taste salty.
Swap in Coffee: Coffee adds deeper chocolate flavor without tasting like coffee.
Let it rest 10 minutes before serving: This helps the sauce thicken slightly while keeping the center warm and spoonable.