01 -
Start by melting your butter and setting it aside so it can cool down a bit. Get your oven heating to 180°C (350°F, or 160°C if you're using a fan oven). Grab two big baking trays and line them with parchment paper.
02 -
In a medium-sized bowl, whisk together your flour, cocoa powder, baking soda, and salt until everything's evenly combined. Set this bowl aside for now.
03 -
In a larger mixing bowl, pour your melted butter over both sugars. Use a whisk to beat them together until they're thoroughly mixed and smooth.
04 -
Crack in your egg and pour in the vanilla extract. Whisk everything together until the mixture looks silky and well blended.
05 -
Pour your flour mixture into the bowl with the wet ingredients. Switch to a spatula and gently fold everything together until you don't see any more dry streaks. Don't overmix—just until it comes together.
06 -
Give your dough a 10-minute break before you start shaping. This little rest makes it way easier to work with and helps your cookies hold their shape better in the oven.
07 -
Scoop out about 2 tablespoons of dough and shape it into a ball. Press your thumb into the center to create a little well, then tuck 6 mini marshmallows inside. Carefully pinch the edges of the dough back together, sealing the marshmallows completely inside.
08 -
Gently roll each stuffed ball between your palms to make it nice and round. Place them on your prepared baking trays, spacing them about 2 inches apart so they have room to spread.
09 -
If you're using the demerara sugar, sprinkle just a tiny bit on top of each cookie. Pop the trays in the oven and bake for 9 to 10 minutes.
10 -
As soon as you pull the trays from the oven, grab a round cookie cutter that's slightly bigger than your cookies. Gently swirl it around each cookie to nudge them into perfect circles and make them a little thicker.
11 -
Let your cookies sit on the trays for about 10 to 15 minutes until they're firm enough to move without breaking. Then transfer them to a wire rack to finish cooling. They'll firm up even more as they cool down.