Preheat oven to 350 degrees. Line 18 muffin tin cups with paper liners and set aside.

In a small bowl, melt butter and chocolate chips together until smooth. Set aside to cool.

In a large bowl, whip eggs, sugar and vanilla extract together until ribbons form and color has changed to a light yellow. Stir in melted chocolate and butter. Sift salt, baking soda, baking powder, cocoa and flour together. Slowly alternate the flour mixture and buttermilk into the butter and chocolate mixture, finishing with buttermilk. Scrape the sides to ensure everything is evenly incorporated. Drop by the heaping tablespoon into the lined cupcake pans. Bake 20-25 minutes or until just cooked through. Set aside to cool completely.

For the peanut butter cookie dough, whip butter and and peanut butter together until evenly incorporated. Stir in remaining ingredients until combined.

Once cupcakes have cooled completely, scoop out a small hole into the center of the cupcakes {about 3/4 inch in diameter and 1/2 inch deep}. Press cookie dough into hole of cupcakes.

For the marshmallow tops, place large marshmallows into a large bowl. Microwave until marshmallows start to melt. Stir together and using well greased fingers, remove about 2 marshmallows worth of fluff and place onto cupcake. Squish marshmallow gently down to cover the top of the cupcake. Re-grease hands and continue to cover the remaining tops of cupcakes.

Once all cupcakes are covered, use a kitchen torch or broiler to toast the tops. Cool slightly and serve.