Instructions

• Prepare 2 cups (470 ml) brewed espresso using the espresso powder according to the powder package directions; transfer to a medium shallow bowl and let it cool to room temperature.
• Set a medium saucepan of water over medium heat until it simmers gently. Place a heatproof glass bowl over the saucepan so the bottom of the bowl does not touch the water (double-boiler setup).
• In the glass bowl, whisk together 6 large egg yolks and ½ cup (100 g) superfine sugar until smooth.
• Place the bowl over the simmering water and whisk constantly for about 8–10 minutes, until the mixture registers 160°F (70°C) on an instant-read thermometer, has thickened slightly, and the sugar has dissolved. Remove the bowl from the heat and let the mixture cool for about 5 minutes (it should be warm, not piping hot).
• In a separate large bowl, beat 16 ounces (450 g) mascarpone cheese with 2 teaspoons (10 ml) pure vanilla extract using an electric mixer until smooth and creamy.
• With the mixer on low, add the warm egg-yolk mixture to the mascarpone in a slow, steady stream (or in a few small additions), mixing until fully incorporated and smooth. This helps prevent curdling. Set the combined custard aside.
• In another clean bowl, whip 2 cups (470 ml) heavy whipping cream with an electric mixer to medium peaks—the peaks should hold but the tips should slightly droop. Do not overwhip.
• Fold the whipped cream gently into the mascarpone–egg custard in two additions, using a rubber spatula and folding motions until uniform and light. Stop as soon as the mixture is homogenous.
• Place 2 tablespoons unsweetened cocoa in a fine-mesh sieve and set aside for dusting later.
• Quickly dip each Oreo cookie once per side into the cooled brewed espresso (a very quick 1-second dip per side; do not soak), and arrange 16 dipped Oreos in a single layer in the bottom of an 8-inch (20 cm) square pan.
• Spread half of the mascarpone mixture evenly over the first Oreo layer.
• Quickly dip the remaining 16 Oreos once per side in the espresso and arrange them in a single layer over the custard.
• Spread the remaining mascarpone mixture evenly over the second Oreo layer and smooth the top.
• Cover the pan with plastic wrap and refrigerate for at least 3–4 hours, preferably overnight, until set.
• Just before serving, dust the top generously with the unsweetened cocoa through the fine-mesh sieve. Cut into 12 pieces and serve.