01 -
In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside.
02 -
In a large bowl, cream the butter with sugar until light and fluffy, about 3-4 minutes.
03 -
Beat in the eggs one at a time, then stir in vanilla extract.
04 -
Gradually mix in the dry ingredients until the dough comes together. Optionally, swirl in marshmallow fluff now or wait until after chilling.
05 -
Cover the dough and refrigerate for at least 1 hour.
06 -
Preheat the oven to 350°F (175°C). Line baking sheets with parchment paper.
07 -
Scoop dough into balls, place them on the baking sheet, and make an indent in the center. Add 1 tsp of marshmallow fluff into each indent.
08 -
Bake for 10-12 minutes, until set around the edges but still soft in the center. Add more fluff halfway through for extra gooeyness.
09 -
Cool cookies on the pan for 5 minutes, then transfer them to a wire rack to cool completely.