Start by preheating your oven to 350°F. Grease an 8×8-inch baking pan with butter, then line it with parchment paper, leaving a little overhang on the sides. That extra parchment makes lifting the brownies out later much easier.

In a medium saucepan, melt ½ cup (115g) unsalted butter over medium heat. Let it cook just until it’s fully melted and beginning to gently sizzle.

Remove the pan from the heat and immediately whisk in 6 oz (170g) semi-sweet chocolate and 1 tablespoon espresso powder. Keep whisking until the mixture is smooth and glossy.

Pour the warm chocolate mixture into a large bowl and add 1¼ cups (250g) granulated sugar. Whisk until combined. The batter may look a little grainy at this stage, and that’s perfectly normal.

Add the 3 eggs one at a time, whisking well after each addition. Once the eggs are fully incorporated, stir in 1 teaspoon vanilla extract, 3 tablespoons vegetable oil, ½ cup (40g) cocoa powder, and ¼ teaspoon salt.

Lastly, add ½ cup (65g) all-purpose flour and mix just until no streaks of flour remain. Be careful not to overmix, as that can make the brownies less tender.

Spread the batter evenly into the prepared pan and bake for 27–32 minutes. The brownies are ready when the top no longer looks wet and a skewer inserted in the center comes out with a few moist, fudgy crumbs but no raw batter.

Let the brownies cool completely in the pan before adding the tiramisu layers on top. This helps everything set properly and keeps the layers neat and stable.

In a wide, shallow bowl, stir together the boiling water, espresso powder, and granulated sugar until everything has fully dissolved. Set the coffee mixture aside and let it cool completely to room temperature.

Once the coffee has cooled, quickly dip each ladyfinger into the coffee—just a quick one-second dunk is all they need. Arrange them in a single layer over the cooled brownie, trimming a few if needed to fit. Be careful not to soak them too long, or they'll become too soft and soggy.

Set the brownie aside while you prepare the creamy topping.

In a large mixing bowl, add the cold mascarpone, powdered sugar, and vanilla extract. Using a hand mixer or a stand mixer fitted with the paddle attachment, beat everything together until the mixture is smooth and creamy.

Keep the mixer on low speed and slowly pour in the cold heavy whipping cream a little at a time. Adding it gradually helps keep the mixture smooth and prevents it from becoming lumpy. Stop after every ¼ cup of cream to scrape down the sides and bottom of the bowl so everything mixes evenly. If it's easier, add just 1 to 2 tablespoons of cream at a time, mixing well before adding more.

Once all of the cream has been incorporated, increase the mixer speed to high and whip for 1 to 2 minutes, or until the mascarpone cream becomes thick, fluffy, and holds stiff peaks.

Spoon the whipped mascarpone cream over the brownie (or ladyfingers) and gently spread it into an even layer.

Refrigerate for at least 1 hour, or until the mascarpone topping is chilled and set.

When you're ready to serve, use the parchment paper overhang to lift the brownie out of the pan and transfer it to a cutting board. Finish with a generous dusting of cocoa powder, then slice and enjoy.