Preheat Oven: Set your oven to 350°F (175°C) and line a baking sheet with parchment paper.
Dissolve Espresso: Mix espresso powder and hot water until dissolved.
Cream Butter and Sugars: In a large bowl, beat butter, brown sugar, and white sugar until fluffy.
Add Wet Ingredients: Mix in egg, vanilla extract, and mascarpone cheese.
Combine Dry Ingredients: In another bowl, whisk flour, baking powder, and salt. Slowly add to the wet mixture.
Add Espresso Mixture: Pour in dissolved espresso and mix until the dough is smooth and slightly sticky.
Shape & Bake: Scoop tablespoon-sized portions onto a baking sheet. Bake for 10–12 minutes, or until edges are golden.
Cool & Glaze: Let cookies cool, then drizzle with glaze and dust with cocoa powder for a tiramisu finish.