Place the flower, the cocoa powder, the butter and the caster sugar in the bowl of a food processor and process until just combined. Add the egg and the vanilla and process again until it forms crumbs. Take the crumbs out of the food processor and use your hands to form the pastry into a ball. Wrap it in a cling film and put in the fridge for 1/2 hours.

Preheat oven to 180°C. Divide the pastry into 12 pieces. Line each cup with the pastry and trim the excess. Prick the pastry with a fork. Line with non-stick baking paper, fill with baking weights or uncooked rice and bake for 15 minutes. Remove the baking paper and weights and bake for 8-10 minutes more until crisp. Set aside to cool.

Prepare the lemon curd. Place 250ml milk and the sugar in a saucepan over medium heat and stir until the sugar is dissolved. Place the cornstarch and remaining milk in a small bowl and stir to combine. Pour into the milk and sugar mixture and stir to combine. Increase heat to high, add the butter and whisk until melted and combined. Add the lemon juice, lemon rind and egg yolks, reduce heat to medium and cook, whisking continuously, for 6–7 minutes or until thickened. Pour the lemon curd into the baked cups and set aside to cool.

Prepare the meringue. Place the egg whites in a bowl and whisk until the egg whites form stiff, white peaks (2-3 minutes approximately). Continue to whisk, gradually add the caster sugar, tablespoon at a time, until the mixture is stiff and glossy (5-10 minutes approximately). Spoon the meringue over the (cooled!) lemon curd. Bake for about 15-18 minutes or until nicely browned.