Instructions

• Make the crust: finely chop the vanilla wafer cookies in a food processor until you have 1 1/2 cups of fine crumbs. Add 2 tablespoons light brown sugar, 1/8 teaspoon fine sea salt, and 1/4 teaspoon ground cinnamon; pulse a few times to combine.
• Melt 6 tablespoons unsalted butter in a microwave-safe bowl (about 45 seconds or until melted). Pour the melted butter into the cookie crumb mixture and fold with a spatula until the crumbs are evenly moistened.
• Transfer the crumb mixture to a 9-inch round tart pan with a removable bottom. Press the crumbs firmly and evenly onto the bottom and up the sides (use a tamper or the bottom of a glass if helpful). Refrigerate at least 30 minutes, or until set.
• Prepare the dulce de leche layer: in a microwave-safe bowl, combine 8 ounces dulce de leche with 2 to 4 tablespoons heavy cream (start with 2 tablespoons and add up to 4 if you need a softer consistency). Microwave for 45 to 60 seconds, stir once, then stir until smooth and the cream is fully incorporated.
• Spread the warmed dulce de leche in an even layer over the chilled crust. Return the tart to the refrigerator while you make the ganache mousse.
• Prepare the ganache base: place 6 ounces finely chopped dark chocolate in a heatproof bowl. In a small saucepan, heat 3/4 cup of the heavy whipping cream until it just begins to bubble (do not boil). Pour the hot cream over the chopped chocolate and let sit 30 seconds, then gently whisk from the center outward until smooth.
• Add the 1/4 cup unsalted butter (cut into chunks) to the melted chocolate, adding one chunk at a time and whisking until each piece is fully incorporated. Stir in 1 teaspoon vanilla extract.
• In a clean bowl, whip the remaining 1/2 cup heavy whipping cream to soft peaks (a slightly softer consistency than typical whipped cream). Gently fold the whipped cream into the chocolate mixture until smooth and no white streaks remain.
• Pour the chocolate mixture over the dulce de leche layer and spread into an even layer. Let the tart set at a cool room temperature for 1 to 2 hours, or refrigerate for 30 to 60 minutes just until set (refrigerating longer may reduce the gloss on top).
• Remove the tart from the pan using the removable bottom, slice, and sprinkle with flake sea salt just before serving. Store covered and refrigerated for up to 2 days. Bring to room temperature before serving.