Salted Caramel Chocolate Tart

STEP 1: MAKE THE CHOCOLATE PASTRY

Sift the flour, cocoa powder and icing sugar into a bowl and stir in the fine sea salt. Rub in the cold butter with your fingertips until the mixture resembles coarse sand, or pulse briefly in a food processor. Add the egg yolks and bring the dough together with as little working as possible, adding a teaspoon of cold water only if it refuses to cohere. Flatten into a disc, wrap and chill for at least 1 hour. The quarter-teaspoon of salt is imperceptible as saltiness but lifts the cocoa, and it is the first of three places the seasoning now appears.

STEP 2: LINE AND BLIND BAKE THE CASES

Roll the pastry to about 3 mm on a lightly floured surface and line the six tartlet tins, pressing well into the corners and leaving a little overhang. Chill for 30 minutes; chilled pastry does not slump. Heat the oven to 170C / 340F. Line each case with parchment and baking beans and bake for 15 minutes, then remove the beans and bake for a further 8-10 minutes until the base is dry and sandy to the touch. Trim the overhang with a small knife while the pastry is still warm, then cool the cases completely.

STEP 3: MAKE THE DEEP SALTED CARAMEL

Put the granulated sugar and water in a heavy-based pan over medium heat and stir only until the sugar dissolves. Stop stirring, raise the heat and let it cook through pale gold and amber to a deep, dark amber - about 180C / 355F on a probe. Off the heat, add the warmed cream in three additions, standing back as it erupts, then whisk smooth and whisk in the butter and the fine sea salt. Taste it on a teaspoon, on its own, now: it should be assertively salted with a faint bitter edge behind the sweetness, and if it is not, add salt a pinch at a time until it is. A caramel that tastes comfortable on its own disappears inside chocolate.

STEP 4: SET THE CARAMEL LAYER IN THE CASES

Divide about 150 g of the warm caramel between the six cooled cases, tilting each to give an even layer roughly 4 mm deep across the base. Scatter the flaky sea salt over the surface while the caramel is still soft, then refrigerate for at least 45 minutes until firmly set. Reserve the rest of the caramel: 60 g for the mousse, 40 g for the hazelnuts and the remainder for the plate. As a discrete stratum the caramel cannot disperse, so every spoonful cuts down through mousse, into caramel, into pastry.

STEP 5: CARAMELISE THE HAZELNUTS

Toast the blanched hazelnuts in a dry pan, or in a 170C / 340F oven for 8-10 minutes, until fragrant and lightly coloured, then chop roughly. Warm 40 g of the reserved caramel, stir the nuts through it and spread them on parchment to cool. Break them up when cold and finish with a pinch of flaky sea salt.

STEP 6: MAKE THE VANILLA ICE CREAM

Warm the milk, cream and split vanilla pod with its seeds to just below a simmer and leave to infuse off the heat for 20 minutes. Whisk the egg yolks, caster sugar and fine sea salt until pale. Pour the warm infusion over the yolks, whisking, then return it to the pan and cook over low heat, stirring constantly with a spatula, until the custard coats the back of a spoon and reaches 82-84C / 180-183F. Strain immediately through a fine mesh sieve into a cold bowl, cool over ice and chill thoroughly, ideally overnight, then churn until thick and firm up in the freezer for at least 2 hours. The base makes more than six quenelles require; the full custard and the long rest are what deliver the smoothness.

STEP 7: MAKE THE CHOCOLATE MOUSSE

Melt the dark chocolate gently and let it cool to about 40C / 104F. Whip the very cold cream to soft peaks, stopping while it still folds like silk rather than butter, and refrigerate it. For the pate a bombe, cook the granulated sugar and water to 118C / 244F, then pour the syrup in a thin stream onto the egg yolks while whisking at speed, and continue until the mixture is pale, thick and cool to the touch. Fold the melted chocolate into the pate a bombe, then fold in 60 g of the reserved salted caramel, then fold in the whipped cream in three additions, losing as little air as possible.

STEP 8: FILL AND CHILL

Transfer the mousse to a piping bag fitted with a plain 12 mm nozzle and pipe it into the chilled cases over the set caramel, filling to just below the rim. Level with a small offset palette knife, or leave a soft piped finish. Refrigerate for at least 3 hours, or overnight. Cold mousse into a cold shell over cold caramel - nothing goes together warm and nothing is rushed.

STEP 9: PREPARE THE RASPBERRIES

Crush half the raspberries lightly with a fork, stir through the caster sugar and lemon juice, and leave them to macerate for 20 minutes. Keep the remaining half whole and cold. Splitting them this way sharpens the acidic counterpoint that a richer, more assertive caramel now calls for.

STEP 10: PLATE AND SERVE

Take the tartlets out of the fridge 10 minutes before serving, then unmould them and set one on each plate. Drag a spoonful of the reserved caramel across the plate or pool a little beside the tart, a fourth point of contact with the flavour. Scatter the caramelised hazelnuts, add the whole raspberries and a spoonful of the macerated ones, then finish with a quenelle of the vanilla ice cream, dipping the pair of quenelle spoons in hot water and drying them between each one. Serve immediately.