01 -
Stir together the flour, cocoa powder, baking soda, and salt in a medium bowl. Keep it aside for now.
02 -
Grab a large bowl and beat the softened butter with the sugar until it’s light and fluffy. This usually takes 3-4 minutes using an electric mixer.
03 -
Add one egg at a time, mixing each in fully before cracking the next. Toss in the vanilla and stir everything together.
04 -
Gently add your dry mix to the wet one in batches, mixing slowly until a dough forms. Don’t overdo it. You can swirl marshmallow fluff in now or save it for later after chilling.
05 -
Wrap the dough up and chill it in the fridge for at least an hour. This helps manage stickiness and reduces spreading when baking.
06 -
Around 20 minutes before baking, preheat your oven to 350°F (175°C). Line two baking sheets with silicone mats or parchment paper to keep the cookies from sticking.
07 -
Roll the cold dough into balls using a spoon or cookie scoop. Place them 2 inches apart on your prepped baking sheets. Make a little dent in each top, fill it with marshmallow fluff, and use a toothpick to swirl it if you want.
08 -
Pop the cookies in the oven and bake for 10-12 minutes. They should be firm on the edges but soft in the middle. For extra gooeyness, you can add some more fluff halfway through.
09 -
Let the cookies rest on the tray for 5 minutes before transferring them to a cooling rack. This makes them easier to move and lets the marshmallow set properly.