For the sweet pastry, cream the butter and sugar together until pale and soft, add the egg and vanilla and mix to incorporate.
Add the sieve flour and mix until a dough is formed.
Turn onto a floured table and form into a ball, wrap in clingfilm and chill for 2 hours.
Once chilled, roll on a floured table until 1/4 inch in thickness.
Grease and flour 6 x 4.5 inch round loose bottom tartlets.
Roll pastry into tins and press down the sides, trim off excess pastry and chill for one hour.
Preheat the oven to 170C.
Once rested line the tart with a square of grease proof and fill with baking beans. Bake for 15 mins or until the tops of the pastry start to turn golden brown. Remove the baking beans and return to the oven and cook for a further 8 minutes or until evenly golden brown.
Remove and set aside to cool
For the chocolate tart filling, heat the milk, cream and orange zest in a pot.
Once warm pour over the chopped chocolate and stir until melted and smooth.
Add the egg and whisk until combined.
Strain into a jug and pour this mix into the pre-baked tart shells. Return to the oven and bake at 100C for 20 minutes or until the chocolate filling is set.
Remove and allow to cool.
When serving I like to dust 1/3 of the tart with cocoa powder, you can serve with a chocolate truffle or simply with a spoon of fresh cream and seasonal berries