Equipment
Ingredients
Chestnut Hazelnut Crust
- 150 g toasted hazelnuts, skins removed
- 100 g sweetened chestnut puree
- 50 g hazelnut flour
- 60 g unsalted butter, melted
- 15 g cocoa powder, sifted
- 2 g kosher salt
Chocolate Mousse Filling
- 250 g bittersweet chocolate (70%), finely chopped
- 150 ml heavy cream, for the ganache base
- 5 g vanilla bean paste
- 250 ml heavy cream, cold, for whipping
Garnish
- 50 g solid bittersweet chocolate block, room temperature
- 20 g roasted hazelnuts, coarsely crushed
- 30 g candied chestnuts, crumbled
Nutrition (per serving)
Method
Preheat the oven to 175°C (350°F). Lightly grease the 23cm tart pan.
Place the toasted hazelnuts in a food processor and pulse until they are finely ground, being careful not to over-process them into a paste.
Add the sweetened chestnut puree, hazelnut flour, melted butter, cocoa powder, and salt to the ground hazelnuts. Pulse until the mixture is evenly moistened and clumps together like wet sand.
Transfer the mixture into the prepared tart pan. Using your fingers or the back of a spoon, press the mixture firmly and evenly across the bottom and up the sides of the pan.
Bake the crust at 175°C (350°F) for 12 minutes until it becomes fragrant and feels set. It will puff slightly during baking but will settle as it cools.
Remove the crust from the oven and allow it to cool completely to room temperature before adding the filling.
Place the finely chopped bittersweet chocolate and vanilla bean paste into a heatproof mixing bowl.
In a saucepan, heat 150ml of heavy cream over medium heat until it just begins to simmer around the edges, reaching approximately 85°C (185°F).
Pour the hot cream over the chopped chocolate and let it sit undisturbed for 2 minutes to gently melt the chocolate.
Using a whisk, gently stir the chocolate and cream starting from the center and moving outward in tight circles until a smooth, glossy ganache forms. Allow the ganache to cool to 35°C (95°F).
In a separate chilled mixing bowl, whip the remaining 250ml of cold heavy cream until soft peaks form. Do not over-whip, or the mousse will become grainy.
Using a spatula, gently fold one-third of the whipped cream into the cooled ganache to lighten the base.
Add the remaining whipped cream in two additions, folding with wide, sweeping motions to incorporate the cream without deflating the air structure.
Pour the chocolate mousse filling into the completely cooled tart shell, using an offset spatula to smooth the top into an even layer.
Transfer the tart to the refrigerator. Chill for at least 4 hours, allowing the cocoa butter in the mousse to crystallize and fully set.
Hold the solid block of bittersweet chocolate firmly and drag a vegetable peeler along the long edge, applying firm pressure to create delicate, rolling chocolate curls.
Just before serving, arrange the chocolate curls generously over the top of the chilled tart. Sprinkle with the coarsely crushed roasted hazelnuts and crumbled candied chestnuts.
Chef's Notes
- Using sweetened chestnut puree (creme de marrons) adds both moisture and structural integrity to the nut-based crust, minimizing the need for added sugars or binders while amplifying the earthy flavor.
- For the cleanest slices and a professional presentation, dip a sharp chef knife into hot water and wipe it completely dry before making each individual cut through the chilled tart.
- The temperature of the ganache base is the single most critical factor in this recipe. If it is too hot, it will melt the whipped cream; if too cold, it will seize into grainy shards. A digital thermometer provides the best insurance.
- Pressing a nut crust can be sticky work. Lightly dampening your fingertips with cold water or using the smooth, flat bottom of a measuring cup helps achieve an even, tightly packed layer without sticking.
Storage
Refrigerator: 3 days — Store in an airtight container to prevent the mousse from absorbing refrigerator odors.
