Preheat oven to 350 F and line baking sheet with parchment paper.

In a large bowl cream together butter and sugars until light and fluffy, about 5 minutes.

Add in vanilla, egg, and egg yolk. Beat until mixture is well combined.

In a second bowl whisk together flour, cocoa powder, baking soda, baking powder, and salt.

Add dry ingredients into wet and mix until just combined.

Fold in the semi sweet chocolate chips.

Scoop 3 tablespoon sized balls of cookie dough and place on the lined baking sheet 2 inches apart.

Bake cookies for 11 minutes or until the tops no longer look wet. Let fully cool on the baking pan.

Once cookies are fully cooled place them on a sheet of parchment paper.

In a medium bowl add marshmallows. Heat in the microwave for 30 seconds and mix until smooth.

Let cool for a few seconds until you can touch it comfortably with your fingers.

Pinch of a piece of melted marshmallow and using both thumbs and index fingers, pinch the marshmallow and pull fingers apart a few times to get a spider web texture.

Gently pull the marshmallow around the cookie, pulling it around the edges so it sticks.

Continue doing this with every cookie.