Ottolenghi’s Chocolate Tart with Hazelnut, Rosemary and Orange

1 If crystallizing the rosemary sprigs for garnishing, lay them flat on a chopping board and, one at a time, lightly brush each side with the egg white. Sprinkle the sugar evenly and lightly over both sides of the leaves, then set aside in a cool, dry place on a wire rack for about 8 hours, until crisp.

2 To infuse the chocolate cream, put the cream, butter, rosemary and orange peel into a small saucepan and place over a low heat. When the mixture is just coming to a simmer and the butter has melted, turn off the heat and set aside to infuse for an hour or two, or overnight in the fridge.

3 Preheat the oven to 220C/200C Fan/Gas Mark 7. To make the ‘brittle’, place the golden syrup, maple syrup, sugar and salt in a small saucepan over a low heat and stir until the sugar has dissolved. Add the hazelnuts and mix until the nuts are evenly coated, then transfer the mixture to a small parchment-lined baking tray and spread the nuts out with a spoon. Bake for 7–8 minutes, until the mixture is golden brown and bubbling, then remove from the oven and allow to cool completely before roughly chopping it into 0.5cm pieces. Set aside until ready to use and turn off the oven.

4 For the pastry, sift together the flour, icing sugar and salt and place in a food processor. Add the butter and lemon zest and pulse a few times, until the mixture has the consistency of fresh breadcrumbs. Lightly whisk together the egg yolk and water and add this to the mix: the dough will feel quite wet, but this is as it should be. Process once more, just until the dough comes together, then tip on to a clean, lightly floured work surface. Lightly knead the dough into the shape of a ball and divide into two equal halves. Wrap each half loosely in cling film and press gently to form two flattish discs. The dough is very soft, so you need to set it aside in the fridge for at least 1 hour (or up to 3 days).

5 To line the tart case, lightly grease your chosen tart tin, either a a 23 or 25cm fluted tart tin with a removable base. When ready to roll out, allow the dough to rest at room temperature for 30 minutes (if it has been in the fridge for more than a few hours) and place on a lightly floured work surface. Tap all over with a rolling pin to soften slightly before rolling out, until it’s about 33cm wide and 4mm thick. Drape the pastry over the tin and gently press it into place, filling any cracks that you have with a little extra pastry. Trim if desired, then place the pastry in the fridge for at least 30 minutes to rest and chill. The remaining pastry can be frozen for future use.

6 To blind bake the tart case, preheat the oven to 200C/180C Fan/Gas Mark 6. Line the tart case with a large piece of parchment paper, covering the base and sides. Fill with baking beans (uncooked rice or pulses also work well) and bake for 20 minutes. Scoop out the beans/rice/pulses, lift off the parchment paper and return the tart to the oven. Bake the pastry, uncovered, for another 6 or 7 minutes, or until lightly golden and dry. Remove from the oven and allow to cool for 10 minutes before sprinkling the chopped hazelnut ‘brittle’ all over the base. Set aside until needed.

7 To make the chocolate filling, place the chocolate in a heatproof bowl set over a pan of simmering water, making sure the base of the bowl isn’t touching the water. Return the infused cream to a low heat and stir gently until hot. Strain the cream over the chocolate (the rosemary and orange peel can be discarded), then stir the chocolate (still over the pan of simmering water) until melted and smooth. Remove the bowl from the pan and set aside.

8 In the meantime, place the egg, yolks and sugar in the bowl of an electric mixer with the whisk attachment in place. Whisk on a medium-high speed for about 4 minutes, until light and thick. Fold a third of this sabayon mix through the melted chocolate, then gently transfer the lightened chocolate mix back into the sabayon. Fold through to fully combine, then scrape the chocolate filling into the tart case, over the hazelnut ‘brittle’. Gently smooth out the top and bake for 12 minutes. Remove from the oven and set aside for 20 minutes or so to cool. Using a tea strainer or small sieve, sift the cocoa powder over the tart just before serving.

If using, garnish with the crystallized rosemary sprigs and serve with some lightly whipped cream, if you like.

Cook's tips:

– The pastry will make more than you need. It will keep well in the fridge, wrapped in cling film, for up to 3 days. It also freezes well, wrapped first in cling film and then aluminium foil, for up to 2 months. If freezing the dough, do so in disc form. The 'brittle' can be made up to 5 days in advance and kept in an airtight container at room temperature, or frozen for up to one month. Don't keep it in the fridge, where it will 'weep'. The infused cream can be prepared up to one day ahead and kept in the fridge. The crystallized rosemary sprigs can be made a day in advance and left at room temperature, uncovered, until ready to serve.

– This can be made in a 23cm or 25cm fluted tart tin with a removable base.

– Once assembled, the tart is best eaten on the day it is baked but it will keep for up to 2 days, stored in an airtight container.