THE DOUGH
1. First of all the dough!
In a food processor or by hand, mix the chopped butter and the flour. Then add the yolks, icing sugar and powder. Finish with the cocoa powder and 4 tablespoons of cold water.
2. Form a ball.
Cover with clingfilm and leave to rest in the fridge for at least 2 hours.
3. Butter and flour a pie tin. Preheat the oven to 180°.
4. Flour your work surface and roll out the pastry. Place it in the tin. Prick the bottom with a fork. Place in the oven for about 15/20 minutes. Once cooked, remove from the oven and set aside.
5. Heat the chocolate, butter and cream in a saucepan over a low heat. Once melted, pour an espresso and add to the mixture. Pour over the tart base and place in a cool place to set.