1. To make the pastry, sift the flour and cocoa into a bowl, add the sugar and the butter and rub the butter in with fingertips or an electric mixer until it resembles fine crumbs.
2. Stir in the egg yolks and gradually bring the crumbs together, squeezing with fingertips and bring together to form a ball. Add a little cold water if needed.
3. Knead the pastry lightly and roll out thinly on a lightly floured surface. Lift the pastry over a rolling pin and then drape into a 24cm (9½in) fluted flan tin that is 2.5cm (1in).deep. Ease the pastry into the flan tin, pressing into the flutes. Trim the pastry a little above the top of the tin with scissors to allow for shrinkage during baking. Prick the base with a fork and chill in the fridge for 30 minutes.
4. Preheat the oven to 190°C/375°F/Gas Mark 6.
5. Transfer the chilled tart tin to a baking sheet, line the pastry case with a large square of non-stick baking paper and fill with baking beans. Cook for 10 minutes. Carefully lift the paper and beans out of the pastry case and cook for 5-10 more minutes until the base is crisp.
5. Meanwhile make the filling – pour the cream and milk into a saucepan, bring just to the boil, take the pan off the heat and add the chocolate. Leave for five minutes until melted. Whisk the eggs, sugar and vanilla together in a bowl until smooth and gradually whisk in the warm chocolate milk.
6. Sprinkle the raspberries over the base of the warm pastry case. Strain the warm chocolate cream into the tart case and cook in the oven reduced to 160°C/325°F/Gas Mark 3 for 25-30 minutes or until just set with a slight wobble in the centre. Leave to cool at room temperature for at 1-1½hours. The tart can be made in advance and chilled in the fridge but the filling will be much firmer when sliced.
7. When ready to serve, remove the tin and transfer tart to a serving plate. Sprinkle a few extra raspberries over the top and decorate with a little sifted cocoa. Cut into slices to serve.
Recipe courtesy of Seasonal Berries