- Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper. 
- In a large bowl, cream the butter, brown sugar, and granulated sugar together until light and fluffy. 
- Add in the egg, vanilla, and espresso. Mix until combined. 
- Stir in the flour, cornstarch, baking soda, and salt until a dough forms. 
- Gently fold in the mascarpone—don’t overmix. We want little pockets of creamy goodness. 
- Scoop the dough into balls and place them a couple of inches apart on your baking sheet. 
- Bake for 9–11 minutes until the edges are set but the centers look slightly underbaked. 
- Let them cool on the baking sheet for 5 minutes before transferring to a wire rack. 
- Dust with cocoa powder once fully cooled. Try not to eat them all in one sitting.