FOR THE PASTRY
200g/1½ cups plain (all-purpose) flour, plus extra for dusting
20g/scant ¼ cup ground almonds
110g/½ cup cold unsalted butter, diced
50g/scant ¼ cup caster (superfine) sugar
1 egg yolk
1 tablespoon cold water
FOR THE BUTTERMILK FILLING
284ml/scant 1¼ cups buttermilk
3 large egg yolks
60g/5 tablespoons soft brown sugar
seeds scraped from 1 vanilla pod
sprig of mint, to garnish (optional)
Preheat the oven to 180°C/350°F/gas mark 4. In the bowl of a food processor combine the flour, ground almonds and diced butter. Process until you have fine crumbs, then add the sugar and mix briefly again.
Next, add the egg yolk and water and pulse until you have something resembling wet sand. Take the mixture and knead gently on a lightly floured surface for 2 minutes, until you have a dough. Then chill it in the fridge, wrapped in cling film (plastic wrap), for at least 30 minutes. Using a rolling pin, roll out the dough to fit a 23cm/9in loose-based tart tin, leaving at least a spare 2.5cm/1in, in case of shrinkage. (The dough is really delicate, so if you struggle rolling it out, try flouring a sheet of baking paper and rolling out on that and then lifting and lowering the rolled out pastry into the tin that way.) Prick the base with a fork to avoid air bubbles. Line the pastry case with baking parchment and fill with baking beans/dried chickpeas and blind bake for
15 minutes before removing the parchment and beans and cooking for a further 10 minutes or until golden. Once out of the oven, run a sharp knife along the edge, trimming the excess if it didn’t fall off on its own during the bake.
For the filling, very gently heat the buttermilk until warm, taking good care that it doesn’t boil or it will curdle. Next, quickly whisk the egg yolks, sugar and vanilla with the warm buttermilk. Place your raspberries in the tart and slowly pour the filling over. Bake for around 30–40 minutes until the filling is golden and cooked through.
Serve cool, with the fresh mint sprig placed in the centre of the tart, if you like.