01 -
Grab a bowl and stir together the salt, baking soda, cocoa powder, and flour until you can't see any lumps.
02 -
Pop your butter and sugar into a big bowl and whip them on high with your mixer until the mix is super light, about 3 or 4 minutes.
03 -
Crack eggs in one after the other, mixing until each disappears before adding the next. Pour in vanilla and mix until it's all worked in.
04 -
Slowly mix the dry stuff into the wet stuff on low. Don't stir too much—stop when you can't see dry bits.
05 -
Gently mix marshmallow fluff through your dough to get lovely swirls, or save it for after chilling if that's your style.
06 -
Wrap up the dough and chill it for at least an hour. It'll get way easier to roll and won't go flat while baking.
07 -
Switch the oven on to 175°C. Cover your trays with silicone mats or parchment so nothing sticks.
08 -
Scoop dough, roll into balls, and set them on your tray with about 5 cm space. Press a dip in each, add a teaspoon of marshmallow fluff and swirl it in with a toothpick.
09 -
Bake them for 10 to 12 minutes. They should look set on the outside but feel a little soft in the middle. Want them extra gooey? Drop in more fluff midway through baking if you're up for it.
10 -
Give the cookies 5 minutes to settle on the tray. Then move them to a wire rack and let them finish cooling so they stay just right.