1-Preheat oven: Preheat oven to 350°F and line two baking sheets with parchment paper.

2-Cream butter and sugars: In a large bowl, cream softened butter, granulated sugar, and brown sugar until light and fluffy, about 2 minutes.

3-Add wet ingredients: Beat in vanilla, salt, espresso powder, egg, and egg yolk until smooth.

4-Combine dry ingredients: In a separate bowl, whisk flour and baking soda, then gradually mix into wet mixture until no streaks of flour remain.

5-Scoop dough: Scoop dough (about 2 tablespoons per cookie) onto prepared sheets, placing dough balls a few inches apart.

6-Bake cookies: Bake for 10-12 minutes until edges are lightly golden and centers look soft.

7-Cool cookies: Let cookies rest on baking sheet for 5 minutes, then transfer to a wire rack to cool completely (warm cookies will melt the cream).

8-Whip cream: In a chilled bowl, whip cold heavy cream with espresso powder, vanilla, and powdered sugar until stiff peaks form; do not overmix.

9-Fold in mascarpone: In a separate bowl, stir room temperature mascarpone to loosen, then fold whipped cream in two additions until smooth.

10-Assemble: Once cookies are completely cool, pipe or spread a generous swirl of mascarpone cream on each.

11-Dust with cocoa: Right before serving, dust cookies with cocoa powder using a fine mesh strainer for even coverage.