Mix the flour, cocoa powder, 110g sugar and a pinch of salt in a bowl. Rub the butter in with your fingertips until the mixture resembles fine breadcrumbs. Stir in the egg yolks and milk and form a dough. Roll into a ball, wrap in cling film and chill for 30 minutes.
Preheat the oven to 180°C, gas mark 4. Put the cranberries, remaining sugar and 2 tbsp water in a saucepan set over a medium heat and cook for 5 minutes, until the cranberries are soft.
Roll out the dough on a floured surface to 3mm thick and use to line the tart tin. Prick all over with a fork and line with baking paper and baking beans.
Bake for 15 minutes. Remove the paper and beans and cook for 12 minutes more, then leave to cool.
Whip together the goats’ cheese and syrup and use to fill the tart. Spoon over the softened cranberries, sprinkle with the chocolate and serve.