White chocolate and raspberry tart with buttermilk pastry
Whisk together the flour, sugar and salt in a mixing bowl. Add the butter, tossing lightly to coat then gently rub it in with your fingertips until the mixture resembles oatmeal. Gradually add the buttermilk, mixing it in with a palette knife, then bring together into a disc. Don’t squeeze or knead. Wrap in greaseproof paper and chill for 30 minutes.
Set the oven to 180°C. Roll out the pastry between 2 sheets of lightly floured greaseproof paper to a thickness of about 3mm, or until wide enough to line the base and sides of a 20cm metal tart tin. When you have finished rolling, gently peel back the top layer of paper. Using a floured rolling pin to help you, peel the pastry off the bottom sheet of paper and drape it over the tart tin. Gently ease the pastry into the tin, pressing it into the base and sides using a small piece of excess pastry rolled into a ball. Roll the rolling pin over the top of the tin to trim away excess pastry. Prick the base all over with a fork, line with foil and baking beans (or use coins, dried beans or uncooked rice), transfer to a baking sheet and blind bake for 10 minutes. Remove the foil and beans and bake for a further 10 minutes, or until pale gold. Beware of overbaking! Set aside in the tin to cool.
Meanwhile, heat the cream and vanilla seeds until very hot, remove from the heat and add the chocolate. Stir off the heat until completely melted. Set aside to cool a little then beat with electric beaters until very thick and pale.
When the pastry has cooled almost completely, spread the chocolate mixture over the base using a palette knife and gently press the raspberries in (in a pretty pattern if it pleases you). Chill for at least a couple of hours to give the chocolate time to set.