1. **Preheat:** Preheat your oven to 350°F (175°C). Line an 8×8 inch square baking pan with parchment paper, leaving an overhang for easy removal.

2. **Make the Brownies:** In a large bowl, whisk the melted butter and granulated sugar until well combined. Beat in the eggs, vanilla extract, and the dissolved espresso mixture.

3. Sift in the cocoa powder, flour, and salt. Fold gently with a spatula just until no dry streaks remain. Do not overmix.

4. Pour the batter into the prepared pan and smooth the top. Bake for 20–25 minutes, or until a toothpick inserted into the center comes out with moist crumbs (not wet batter).

5. **Cool & Soak:** Remove brownies from the oven. While still warm, gently brush the top with the coffee/Kahlua mixture (if using). Let the brownies cool completely in the pan. **Crucial:** They must be 100% cool before topping, or the cream will melt.

6. **Make the Topping:** In a medium bowl (or stand mixer), whip the cold heavy cream, powdered sugar, and vanilla until stiff peaks form.

7. In a separate bowl, gently stir the mascarpone cheese to loosen it (don’t overbeat or it can curdle). Gently fold the whipped cream into the mascarpone until smooth and combined.

8. **Assemble:** Spread the mascarpone cream evenly over the completely cooled brownies.

9. **Chill:** Refrigerate for at least 2–3 hours to let the topping set firmly.

10. **Serve:** Lift the brownies out of the pan using the parchment handles. Generously dust the top with cocoa powder using a fine mesh sieve. Slice into squares and serve.