Chocolate truffle tart with mascarpone cream. Start by processing the flour, icing sugar, cocoa and butter in a food processor until the mixture resembles bread crumbs. Add the egg yolk and water, process until the dough comes together. Turn onto a floured surface and knead until just smooth. Shape the dough into a disk and cover with plastic wrap. Pop the dough in the fridge for 30 minutes to rest. Roll between two sheets of baking paper to a 15 cm by 40 cm rectangle. Then line a 10 cm by 34 cm rectangular tart tin with a removable base with the pastry. Use a knife to trim the edges. Place in the fridge for 15 minutes to chill. Next, preheat the oven to 200 degrees Celsius. Place the tart on a baking tray and line with baking paper and fill with pastry weights on rice. Bake for 10 minutes. Remove the paper and weights and bake for a further 8 to 10 minutes or until the pastry is dry to touch. Remove the pastry from the oven then reduce the oven to 150 degrees Celsius. While the pastry’s in the oven, place the chocolate and cream in a heatproof bowl over a pan of simmering water for 5 minutes or until the chocolate melts and the mixture is smooth. Set aside for 5 minutes to chill slightly. Whisk in the eggs. Pour the chocolate into the pastry case and bake for 20 to 25 minutes or until just set that aside to cool slightly. The0,n pop in the fridge for 2 hours to chill. To make the mascarpone cream, use an electric mixer to whisk the cream, mascarpone, icing sugar and liqueur syrup in a bowl until soft peaks form. Divide into 3 portions. Then, add enough cocoa powder to 2 portions to tint one light and one dark brown. Place the mascarpone cream portions into separate piping bags - one fitted with a plain nozzle and two fitted with fluted nozzles. Pipe mascarpone cream over the tart, alternating between the colours. Place on a serving plate and sprinkle with raspberries cut into pieces to serve. This stunning chocolate tart is a perfect finish to any celebration.