Follow these clear steps to create your Tiramisu Brownies:

1. Preheat Oven: Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish or line it with parchment paper.

2. Melt the Butter: In a medium saucepan, melt the unsalted butter over low heat. Once melted, remove from heat and let it cool slightly.

3. Mix Sugar and Eggs: In a large bowl, combine the granulated sugar and eggs. Whisk until the mixture is thick and pale.

4. Add Butter and Vanilla: Stir in the melted butter and vanilla extract until well combined.

5. Combine Dry Ingredients: In a separate bowl, whisk together the all-purpose flour, cocoa powder, baking powder, and salt.

6. Combine Mixtures: Gradually add the dry mixture to the wet ingredients. Stir until just combined. Be careful not to overmix.

7. Fold in Chocolate Chips: Gently fold in the semi-sweet chocolate chips for added richness.

8. Bake Brownies: Pour the brownie batter into the prepared baking dish. Spread evenly and bake for 30-35 minutes. A toothpick should come out with a few moist crumbs when done.

9. Cool the Brownies: Allow the brownies to cool completely in the baking dish on a wire rack.

10. Prepare the Tiramisu Layer: In a mixing bowl, whip the heavy cream until soft peaks form. Add the mascarpone cheese, powdered sugar, and vanilla extract. Mix until smooth and fluffy.

11. Prepare Coffee Mixture: In another bowl, combine the cooled espresso (and coffee liqueur if using).

12. Layer the Tiramisu: Once brownies are completely cooled, brush the mixture of espresso over the top. Spread the mascarpone mixture evenly over the brownies.

13. Chill: Cover and refrigerate the brownies for at least 2 hours. This will allow the layers to set and flavors to meld.

14. Dust with Cocoa Powder: Before serving, dust the top with cocoa powder for a classic tiramisu finish.

These straightforward steps will guide you in producing Tiramisu Brownies that are both delicious and visually appealing!