Turn on stove to medium heat. Add chocolate chips and peanut butter. Stir together with whisk until melted and smooth. Be careful not to let it get too hot or it will harden.

Very slowly, whisk in milk. The slower you do it, the easier it will be to incorporate into the chocolate-peanut butter mixture. Keep whisking until all the chocolate is mixed into the milk. This may take 1-2 minutes.

Add in cocoa powder and whisk until mixed into milk mixture.

Keep cooking until the mixture begins to froth on top. Check temperature. If full warmed-through, turn off heat and serve. Top with marshmallows and chocolate sauce and/or melted peanut butter. You can also add chopped peanut butter cups.