Pâte a tarte au cacao (Sweet chocolate tart pastry)

Method
Prep:10min  ›  Cook:20min  ›  Extra time:1hr chilling  ›  Ready in:1hr30min 

1. In a bowl, beat vigorously with a fork, the oil, the milk, the sugar and the salt.
2. When the sugar is dissolved, add (still beating with a fork) the melted butter, the egg yolk and the cocoa powder. The mixture should form a paste.
3. Stir in the flour 1 tablespoon at a time using a spatula until the dough is a soft, homogeneous paste-like texture.
4. Roll into a ball, wrap in cling film and chill in the fridge for at least an hour.
5. Preheat the oven to 170 C / Gas 3.
6. Take the dough out of the fridge and deposit the ball in the centre of a 20-24cm flan tin. The dough is not rolled but spread by hand. Flatten in all directions to the edge with care. It should go well beyond the sides as it will shrink when cooking.
7. Bake in a preheated oven for 20 minutes at 170 C / Gas 3. Either prick the base with a fork or "bake blind" with baking beans.
8. Remove from the oven and leave to cool at room temperature.