Chocolate Hazelnut Tart — praline crunch under a gianduja ganache

i. Origin & history

The pairing of chocolate and hazelnut is Piedmontese. In nineteenth-century Turin, then one of Europe's great chocolate-making cities, confectioners began blending finely ground local hazelnuts into chocolate to create gianduja — a smooth, soft, intensely nutty chocolate. The story often told is that the hazelnuts stretched cocoa when it was scarce and expensive, perhaps during the Napoleonic era's trade blockades. The name comes from Gianduja, a carnival character and folk symbol of Turin, and the boat-shaped gianduiotto chocolate became one of the city's emblems.

In the twentieth century the same idea took a commercial turn. In the Piedmontese town of Alba, the Ferrero family produced a sliceable chocolate-hazelnut paste after the Second World War, which evolved into a spreadable cream and, in 1964, was launched as Nutella. The flavour became familiar around the world.

French pastry chefs took the pairing in their own direction, through praliné — caramelised hazelnuts ground into a paste — and its crunchy cousin, the praliné feuilletine, a mixture of praline paste, chocolate and crushed wafer flakes that became a staple layer in French entremets from the late twentieth century. The chocolate-praline tart combines these elements with the classic French chocolate tart, the tarte au chocolat.

Today it is a standard of modern French pâtisserie and a favourite with home bakers, appearing in pastry shops in individual and whole versions, often finished with gold leaf, cocoa nibs or caramelised hazelnuts.

ii. How the crunch layer stays crisp under ganache

The surprise in this tart is the thin crunchy layer at the bottom. It is made from praline paste, melted chocolate and feuilletine — tiny flakes of crisp, buttery wafer. Normally, a crisp element sitting under a moist filling goes soft within hours. Here it stays crunchy for days because the wafer flakes are coated in fat: the cocoa butter and nut oils in the chocolate and praline seal each flake, so moisture from the ganache cannot reach it. The same principle explains why chocolate-coated wafers stay crisp in their wrapper.

The ganache is the second key. A classic chocolate tart ganache uses roughly equal weights of dark chocolate and cream. Adding praline paste introduces extra oil and sugar, which softens the set, so the proportion of chocolate is kept relatively high and the ganache is made with a 60–70% dark chocolate. The result is a filling that slices cleanly but melts on the tongue.

The ganache must be emulsified properly. Pouring hot cream over chopped chocolate and stirring gently from the centre outwards — or blending with a stick blender held below the surface — creates a smooth, glossy emulsion in which fat droplets are evenly suspended in the water from the cream. Whisking vigorously traps air bubbles, and adding cold praline to hot ganache can make it split. Warming the praline paste slightly first helps.

Finally, the cocoa pastry has to be baked fully and cooled before anything goes in. Cocoa makes it harder to judge colour, so bake by time and touch: it should feel dry and firm and smell toasty.

iii. Ingredients

Makes 10 servings · scroll the side panel to adjust

• 180 g plain flour
• 25 g cocoa powder
• 70 g icing sugar
• 1 pinch salt
• 110 g cold unsalted butter, diced
• 1 egg
• 60 g hazelnut praline paste, for the crunch layer
• 30 g milk chocolate, melted
• 40 g feuilletine flakes or crushed crêpes dentelle
• 200 g dark chocolate (60–70% cocoa), chopped
• 250 ml double cream
• 80 g hazelnut praline paste, for the ganache, at room temperature
• 20 g unsalted butter, soft
• 60 g blanched hazelnuts, toasted and halved
• ½ tsp flaky sea salt

Hazelnut praline paste is sold by specialist baking suppliers, or make it by caramelising toasted hazelnuts and blending them to a runny paste (see hazelnut praline). Feuilletine is sold in bags by pastry suppliers; crushed French crêpes dentelle biscuits are the classic substitute, and crushed cornflakes work in a pinch. Use a good dark chocolate between 60% and 70%; higher percentages make a firmer, more bitter ganache. If you cannot find praline paste, a smooth unsweetened hazelnut butter with an extra tablespoon of sugar is an acceptable stand-in.

iv. Method

1. For the pastry, rub the flour, cocoa, icing sugar, salt and cold butter to fine crumbs, add the egg and bring together into a dough. Flatten, wrap and chill for 1 hour.
2. Roll the pastry 3 mm thick and line a 23 cm loose-bottomed tart tin. Prick the base and chill for 20 minutes. Heat the oven to 180 °C (350 °F), fan 160 °C.
3. Blind-bake with paper and beans for 15 minutes, then remove them and bake 8–10 minutes more, until the base feels dry and firm and smells toasted. Cool completely.
4. For the crunch layer, mix 60 g praline paste with the melted milk chocolate, then stir in the feuilletine. Spread in a thin, even layer over the base of the cooled case. Chill for 10 minutes to set.
5. For the ganache, bring the cream just to the boil and pour it over the dark chocolate. Leave for 2 minutes, then stir gently from the centre outwards until smooth. Add the 80 g praline paste and the butter and stir, or blend with a stick blender held below the surface, until glossy.
6. Pour the ganache over the crunch layer, tilting the tin to level it. Pop any bubbles with a cocktail stick.
7. Leave at room temperature for 30 minutes, then scatter over the toasted hazelnuts and a pinch of flaky salt. Chill for at least 2 hours until set.
8. Remove from the fridge 20–30 minutes before serving. Slice with a knife dipped in hot water and wiped dry.

v. Tips & common mistakes

• Keep the crunch layer thin. A thick layer is hard to cut and overwhelms the ganache. Three or four millimetres is enough.
• Stir the ganache, do not whisk. Gentle stirring or a submerged stick blender gives a glossy, bubble-free surface.
• Warm the praline first. Cold, stiff praline paste can make the ganache seize or split. Room temperature is fine.
• Bake cocoa pastry by feel. Its colour hides doneness. It should be dry, firm and smell toasted, not raw.
• Add hazelnuts once the ganache has thickened. Added straight away, they sink into the filling.
• Serve just cool. Straight from the fridge the ganache is firm and muted; 20–30 minutes out gives a silky texture.

vi. Variations

For a gianduja tart, replace half the dark chocolate with milk gianduja chocolate for a softer, sweeter filling. A salted caramel and hazelnut tart adds a thin layer of caramel over the crunch base. Use a plain pâte sucrée instead of cocoa pastry for a lighter look, or replace the hazelnuts with almonds and almond praline. Individual tartlets set faster and are easier to serve.

Related desserts include the praline tart of Lyon (a very different, pink-almond tart), the Paris-Brest and the hazelnut mousse. For coconut instead of hazelnut, try the chocolate coconut tart, and for hazelnut and chocolate in frozen form, the Italian tartufo.

vii. Serving & storage

Serve thin slices, as the tart is very rich, with crème fraîche, lightly whipped cream, vanilla ice cream or a few raspberries for sharpness. A small cup of espresso is the natural partner. It is an ideal dinner-party dessert because it must be made ahead and keeps well.

Keep the tart covered in the fridge for up to 4 days; the crunch layer stays crisp throughout. Bring it to room temperature for 20–30 minutes before serving. The pastry case can be blind-baked up to 2 days ahead. The finished tart freezes well for up to a month, wrapped tightly; thaw overnight in the fridge. The ganache may lose a little of its shine.

ix. More from French

• Hazelnut Praline — the pastry-kitchen praliné
• Hazelnut Mousse — praline mousse
• Paris-Brest — praline cream choux ring
• Chocolate Coconut Tart — coconut under ganache
• Praline Tart — Lyon's pink tart
• Tartufo — Italian frozen truffle