01 -
In a medium bowl, stir together the flour, cocoa, baking soda, and salt until well blended. Put aside for later.
02 -
In a big bowl, beat the softened butter with sugar using an electric mixer. Keep at it until it's fluffy and airy, which should take 3-4 minutes.
03 -
Mix in the eggs one at a time, making sure each one gets completely blended before the next. Stir vanilla in after that.
04 -
Slowly pour the dry mix into the wet mix, running the mixer on low just until the dough forms. Don’t overdo it. You can gently stir in the marshmallow cream now or later after cooling the dough.
05 -
Cover the dough with plastic wrap and pop it in the fridge for at least an hour. This helps with shaping and keeps the dough from spreading too much while baking.
06 -
Turn your oven on to 350°F (175°C) about 20 minutes before baking. Line two baking trays with parchment paper or silicone mats.
07 -
Scoop up chilled dough with a tablespoon or cookie scoop and roll it into balls. Lay them on the trays about 2 inches apart. Press a dip into the middle of each ball, then fill the dip with marshmallow cream. Use a toothpick to swirl it around.
08 -
Bake on the middle rack of the oven for 10-12 minutes. Keep an eye out—edges should look set but the center should stay soft. Toss in a bit more marshmallow cream halfway through if you like extra gooey.
09 -
Leave the cookies on the trays to cool for 5 minutes. This helps the marshmallow firm up a bit. Then move them to a wire rack.