01 -
Preheat oven to 350°F (176°C). Line a baking sheet with parchment paper.
02 -
Combine the flour, cocoa powder, baking soda and salt in a medium sized bowl and set aside.
03 -
Cream the butter and sugars together until light and fluffy, about 2-3 minutes.
04 -
Add the egg and mix until well combined. Add the egg yolk and vanilla extract and mix until well combined.
05 -
Add the dry ingredients and mix until well combined. Do not over mix.
06 -
Scoop 1 1/2 tbsp (25g) sized balls. Place the cookie dough balls on the lined cookie sheet. Bake for 5-6 minutes, or until the edges are just set, but they don’t look fully baked. They will still be a touch glossy and rounded. Open the oven and carefully add half a marshmallow on top of each cookie, working quickly.
07 -
Bake for 2-3 more minutes or until the marshmallows are soft and just before the cookies begin to brown. The cookies should look flatter and baked.
08 -
Remove from the oven and press marshmallow down slightly. Let cool for 3-4 minutes, then remove to a cooling rack to finish cooling.
09 -
After the cookies have cooled, add the chocolate to a microwave-safe bowl and heat in 10-15 second increments, stirring well between each, until fully melted.
10 -
Spoon about a tablespoon of chocolate onto each cookie and spread so that the marshmallow is fully covered. Allow to cool completely, then serve.
11 -
Store leftovers in an air-tight container. Cookies are best if eaten within 4-5 days.