Preheat oven to 350 degrees F. Liberally grease 8 cavities in a standard-size muffin pan with cooking spray; set aside.
Open the can of biscuits and cut each biscuit into three equal pieces (think of a peace sign to help get them equally-sized). Flatten each piece with the heels of your hands and set aside for a moment.
Take three miniature marshmallows and dip them into a bowl of melted butter, coating them gently. Remove them with a slotted spoon and drop them into the bowl of cinnamon sugar, dredging them until they're coated in cinnamon sugar.
Place a miniature marshmallow in the middle of each biscuit piece. Pinch the biscuit together to completely enclose the marshmallow inside. Once the marshmallow is filled within the biscuit piece, gently coat the biscuit pieces in the butter, then roll them carefully in the cinnamon sugar. Place three biscuit pieces into one muffin cavity - that's one monkey bread muffin. Repeat with remaining marshmallows and biscuits.
Bake for approx. 11-15 minutes or until muffins are golden and bubbly. Remove from the oven and allow them to set briefly, about 5-10 minutes, before serving. You can enjoy these at room temperature, but I prefer them warm. This recipe is very easily doubled!