Preparation

Make the crust

• Lightly grease an 8×8-inch straight-sided baking pan with cooking spray or softened butter. Line the bottom and sides with heavy-duty aluminum foil, leaving some foil overhanging two opposite ends of the pan by a couple of inches. Grease the foil. Set aside.
• Put the gingersnaps, brown sugar, and salt in the bowl of a food processor, and process until finely ground, about 1 minute. Reserve 2 Tbs. of the hazelnuts. Add the remaining hazelnuts to the processor, and pulse to finely chop, about 15 pulses. Add the melted butter, and process, scraping down the bowl with a silicone spatula if necessary, until the crumbs are uniformly moistened.
• Transfer the crumbs to the prepared pan, and firmly press them into the bottom and up the sides, making the bottom slightly thicker than the sides. After pressing with your fingers, use a measuring cup or straight-sided glass to tightly secure the crumbs into place. Freeze the crust for at least 1 hour and up to overnight.

Make the filling and assemble the pie

• Chill a stand-mixer bowl and paddle attachment, about 15 minutes. Put the mascarpone, confectioners’ sugar, and salt in the chilled bowl, and mix briefly with the chilled paddle on low to combine and break up the mascarpone, scraping down the bowl with a silicone spatula as needed. In a separate large chilled bowl, whip the cream and vanilla until medium peaks form.
• Gently fold the whipped cream into the mascarpone in two additions with a large silicone spatula. Once fully combined, transfer the filling to the prepared crust, smoothing the top with an offset spatula or butter knife. Cover the cake with plastic wrap, and refrigerate at least 5 hours, preferably overnight.

Serve the pie

• Chop the remaining 2 Tbs. hazelnuts. Grasp two sides of the foil, and lift the pie from the pan. Using a couple of large spatulas or one large spatula, lift the pie off the foil and onto a cutting board. Using a long serrated knife, cut the pie into 16 pieces. Run the knife under hot water before each cut to ensure clean slices. Garnish each piece with a slice or two of fig and some of the chopped hazelnuts before serving.