A chocolate crémeux sits atop a crumble base, which gives a fantastic texture. It is served with lime butterscotch sauce, a quenelle of hazelnut ice-cream, and a few caramelised hazelnuts.

The crémeux should be made at least six hours ahead – and if required, the dessert can be completed a day in advance.

Serves 8 

Ingredients
For the crumble base:
• 35g cold unsalted butter
• 35g demerara sugar
• small pinch of salt
• 30g plain flour
• 1½ tsp cocoa powder

For the chocolate crémeux:
• 155g good-quality 70% dark chocolate, chopped
• 1 organic free-range egg
• 90ml whipping cream
• 150ml whole milk

For the caramelised hazelnuts and ice-cream:
• 400g whole skin-on hazelnuts
• 40ml water
• 180g caster sugar
• pinch of sea salt
• 400ml milk
• 100ml whipping cream
• 6 organic free-range egg yolks (approximately 120g)

For the lime butterscotch sauce:
• 180ml whipping cream
• 40ml water
• 180g caster sugar
• 75g freshly squeezed lime juice, heated
• 5g finely grated lime zest
• 10g fresh ginger, peeled and finely grated
• sea salt and freshly ground black pepper

Ingredients
1 For the crumble base, preheat the oven to 170°C. Stand an 18cm tart ring on a baking tray lined with greaseproof paper. Pulse all the ingredients together in a food processor for a few seconds, to a crumble texture.
2 Sprinkle the crumble evenly into the tart ring, and press down lightly. Bake for 10–12 minutes. Remove from the oven and set aside to cool.
3 For the crémeux, melt the chocolate in a bain-marie. Lightly beat the egg in a medium bowl. Bring the cream and milk to the boil, then pour onto the egg, whisking all the time. Slowly whisk this mixture into the melted chocolate. Leave to settle; skim off any bubbles. Pour the chocolate mixture over the crumble base in the tart ring. Let cool for 30 minutes, then refrigerate for 6–24 hours.
4 For the caramelised hazelnuts, preheat the oven to 180°C. Scatter the nuts on a baking tray and roast for 10 minutes. Leave to cool, then wrap the nuts tightly in a cloth and rub to remove the skins. Pick out the nuts and set aside.
5 Put the water in a medium pan, add 100g of the sugar, and leave for a few minutes. Heat, stirring, to melt the sugar and cook to a dark caramel. Carefully add the hazelnuts and salt, turn the nuts with a spoon to coat in the caramel, then tip onto a greased tray and leave to cool for 1 hour.
6 When the caramelised hazelnuts are set firm, break them up. Put 250g into a food processor and pulse to a coarse texture; do not grind to a powder. Set aside. Reserve the remainder for decoration.
7 For the ice-cream, freeze the bowl of your ice-cream machine. Warm the milk and cream in a medium saucepan over a medium heat.
8 Meanwhile, in a large bowl, cream the egg yolks and remaining 80g sugar together until the mixture is pale. Whisk in the hot creamy milk, then pour back into the pan and stir over a medium heat until the custard is thick enough to coat the back of a wooden spoon. Stir in the 250g ground hazelnuts. Pour into a bowl and set over ice to cool quickly, then churn in the ice-cream machine for 25 minutes, or until thick.
9 For the sauce, bring the cream to the boil in a small pan. Put the water into another, large saucepan, add the sugar and leave for a few minutes. Heat, stirring, to melt the sugar evenly, then let it colour to an amber caramel.
10 Carefully pour in the hot lime juice, lime zest and grated ginger, followed by the hot cream; it will bubble fiercely. Stir well and bring back to the boil. Cook for 3–4 minutes until thick enough to coat the back of a spoon. Add a pinch each of salt and pepper. Let cool, then refrigerate.
11 To serve, once the chocolate crémeux has set, warm the ring with a cook’s blowtorch and lift it from the tart. With a warm knife, cut the tart into slices. Top with a quenelle of hazelnut ice-cream, and serve with the lime butterscotch sauce and a scattering of caramelised hazelnuts.

Recipe courtesy of Raymond Blanc