Creating Tiramisu Brownies is as straightforward as following these simple steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking pan 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 the heat and let it cool slightly.

3. Combine Sugars: In a large mixing bowl, whisk together the granulated sugar and brown sugar. Add the melted butter and stir until well combined.

4. Add Eggs: Beat in the eggs, one at a time, mixing well after each addition. Then, stir in the vanilla extract.

5. Mix Dry Ingredients: In another bowl, sift together the flour, cocoa powder, and salt.

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

7. Add Chocolate Chips: If desired, fold in the semi-sweet chocolate chips for an extra touch of chocolate.

8. Bake the Brownies: Pour the brownie batter into the prepared baking pan and spread it evenly. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.

9. Cool the Brownies: Once baked, remove the brownies from the oven and allow them to cool in the pan for at least 15-20 minutes before transferring to a wire rack to cool completely.

10. Prepare the Tiramisu Layer: In a large bowl, beat the mascarpone cheese until smooth. In another bowl, whip the heavy cream with powdered sugar and vanilla extract until stiff peaks form.

11. Combine Layers: Gently fold the whipped cream into the mascarpone mixture until fully combined.

12. Add Coffee: Stir in the brewed coffee gently into the mascarpone mixture, being careful not to deflate the whipped cream.

13. Assemble the Dessert: Once the brownies have cooled completely, spread the mascarpone mixture evenly over the brownies.

14. Dust with Cocoa: Sift cocoa powder over the top of the tiramisu layer for a finishing touch.

15. Chill and Serve: Allow the brownies to set in the fridge for at least 30 minutes before cutting into squares and serving.