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)
Nutrition is estimated per serving. Nutrients without complete source data are omitted.
Full nutrition
- Calories
- 519 kcal
- Protein
- 7 g
- Carbohydrates
- 31 g
- Fat
- 43 g
- Fiber
- 6 g
- Sugar
- 17 g
- Sodium
- 97 mg
- Saturated Fat
- 19 g
- Trans Fat
- 1 g
- Monounsaturated Fat
- 16 g
- Polyunsaturated Fat
- 3 g
- Cholesterol
- 60 mg
- Potassium
- 460 mg
- Calcium
- 76 mg
- Iron
- 3.8 mg
- Magnesium
- 96 mg
- Phosphorus
- 178 mg
- Zinc
- 1.4 mg
- Vitamin A
- 206 mcg
- Vitamin C
- 5 mg
- Vitamin D
- 0.6 mcg
- Vitamin E
- 3.3 mg
- Vitamin K
- 8 mcg
- Vitamin B6
- 0.2 mg
- Vitamin B12
- 0.1 mcg
- Thiamin
- 0.16 mg
- Riboflavin
- 0.14 mg
- Niacin
- 0.8 mg
- Folate
- 31 mcg
- Water
- 31 g
- Alcohol
- 0 g
- Caffeine
- 18 mg
Sources: Aggregated Public Data, USDA FoodData Central
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.
Troubleshooting
Mousse turns grainy or splits when folding in the whipped cream
Cause: The chocolate ganache base was too cold, causing the cocoa butter to seize when introduced to the cold cream.
Fix: Place the mixing bowl over a warm water bath for 10 seconds while gently whisking to remelt the fat, though some volume will inevitably be lost.
Prevention: Ensure the chocolate mixture is between 30 and 35 degrees Celsius before beginning the folding process.
Chocolate curls splinter into tiny shards instead of rolling
Cause: The chocolate block is too cold.
Fix: Warm the block very briefly in your hands or microwave it on a defrost setting for 3 to 5 seconds to soften the cocoa butter slightly.
Prevention: Allow the chocolate block to sit at room temperature for an hour before shaving.
Cultural Context
The pairing of chocolate and chestnut, known as chocolat et marron, is a quintessential French winter flavor profile often found in classic alpine desserts like the Mont Blanc. Hazelnuts introduce an earthy, roasted dimension that brilliantly bridges the gap between the dense, sweet chestnut puree and the bitter complexity of high-percentage dark chocolate. This tart reimagines those traditional comforting flavors into a sophisticated, textural contrast of airy modern mousse and crisp, rustic crust.
