Preheat oven to 425 degrees. Grease two 8 oz. ramekins. Place 1 tablespoon flour into each ramekin. Tap the flour around to coat the ramekin and discard any of the remaining flour that didn't stick.

In a microwave-safe bowl, add in the chopped baking chocolate, peanut butter, and butter. Microwave in 30 second intervals and stir after each 30 seconds. Do this 3 to 4 times until the chocolate is smooth and completely melted.

Let cool for about 10 minutes so it doesn't cook the eggs when they're added.

Add in the sugar and eggs and whisk until combined.

Add in the 4 remaining tablespoons of flour and whisk until just incorporated.

Pour the batter evenly into the two 8 ounce ramekins.

Add 1/4 cup of marshmallow fluff to the center of each ramekin. Spoon some of the batter in the ramekin over top of the fluff to cover it slightly.

Place the ramekins on a baking sheet and place into the preheated oven. Let bake for 14 - 16 minutes. You'll want the center to be slightly jiggly and the marshmallow fluff on top toasted.

Serve immediately in the dish. No need to dump onto another plate.