Preheat the oven to 375°F. Line a large cookie sheet with parchment paper.
In a medium bowl, use a nonstick spatula to mix the melted butter and sugar
Add in the egg+yolk and mix. Add in your extracts and mix until homogenous.
Add in flour, baking soda, and salt. Fold mixture to combine.
Dough will be thick!
Dollop lemon curd in 1/2 tablespoon sized portions into dough.
Dollop fluff in same fashion. Swirl knife through dollops and dough to create a swirled effect. You do not want to add too much marshmallow or fluff since they will melt in the oven and burn if they melt onto the cookie sheet itself.
Scoop cookies using a 2 oz scooper. Try to get the fluff and curd at the top of the cookie in your scoop. As you scoop, you will need to re-layer some curd and fluff so every scoop has some! Place scoops on your parchment-lined sheet and place in freezer for two hours.
Remove from freezer. Bake cookies for 10-13 minutes in the oven. If they don't look perfect, do not fret! Use a round cookie cutter or cup to shape them into perfect circles while they are warm right out of the oven. Also, top with just a little bit more fluff and curd for a pretty cookie! Let cool for another 10. Enjoy!