1. Making the Cookie Dough

1. In a large mixing bowl, combine softened butter, granulated sugar, brown sugar, vanilla extract, kosher salt, and espresso powder. Use an electric hand mixer to blend until smooth and creamy.
2. Add the egg and egg yolk, mixing thoroughly until the mixture becomes creamy and well incorporated.
3. Gradually add the flour and baking soda, blending with the hand mixer until just combined. Avoid overmixing to maintain the dough’s soft texture.

2. Baking the Cookies

1. Use a large cookie scoop or two tablespoons to shape the dough into even-sized portions. Place them on a baking sheet lined with parchment paper.
2. Bake in a preheated oven at 180°C (350°F) for 10–12 minutes, or until the edges are lightly golden.
3. Remove from the oven and let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack.

3. Preparing the Mascarpone Cream

1. In a large mixing bowl, combine heavy cream, espresso powder, vanilla extract, and powdered sugar. Use an electric hand mixer to whip the mixture until stiff peaks form. Be careful not to overwhip.
2. Add the room-temperature mascarpone cheese and gently fold it into the whipped cream using a spatula. Mix lightly until smooth and creamy.

4. Assembling the Cookies

1. Transfer the mascarpone cream into a piping bag fitted with a round tip.
2. Pipe the cream onto each cooled cookie, creating a generous swirl on top.
3. Dust with cocoa powder for the finishing touch and serve immediately.