01 -
Set the oven to 190°C and line baking sheets with parchment paper.
02 -
Whisk together flour, baking soda, and salt in a medium bowl until evenly mixed.
03 -
Using a mixer, beat softened butter with granulated and brown sugar until light and fluffy, about 2-3 minutes.
04 -
Incorporate the eggs one at a time, then blend in the vanilla extract until fully combined.
05 -
Mix the cocoa powder with milk and espresso powder if using, until a smooth paste forms.
06 -
Gradually add dry ingredients to the butter mixture, mixing until just combined. Fold in chocolate chips and gently swirl in the cocoa paste.
07 -
Carefully fold in the mini marshmallows to avoid breaking them, ensuring even distribution.
08 -
Scoop dough onto prepared sheets, spacing cookies adequately. Bake for 9 to 11 minutes until edges are set but centers remain soft.
09 -
Allow cookies to rest on baking sheets for 5 minutes before transferring to a wire rack to cool completely.