1. In a large mixing bowl, beat together the butter and icing sugar until light and fluffy then add the eggs one at a time and beat into the butter and sugar mixture until smooth.
2. Tip in the flour and cinnamon and mix to a smooth paste that doesn’t stick to the bowl’s side. Mould into a ball, wrap in cling film and place in the fridge for at least 2 hours.
3. Preheat the oven to 220C/Gas 7.
4. Remove the pastry from the fridge and roll it out on a floured worktop until it is the thickness of a pound coin approximately. Using your rolling pin, life the dough and lay it over a 28cm flan tin, easing it into the edges carefully. Trim off any excess dough from the sides.
5. Line the inside of the pastry with baking parchment and then fill with baking beans (or rice if you don’t have any) and then blind bake for 15 minutes until the pastry is golden. Remove the paper and beans and then bake for a final 5 minutes to brown the centre of the tart case.
6. Reduce your oven to 120C/Gas ¼.
7. Now you need to crack on with the filling: Tip your chocolate into a heatproof bowl. Bring your milk and cream to the boil then pour it over the chocolate whisking quickly to form a smooth and shining mixture.
8. Stir in the eggs and orange juice and then pour into your tart case.
9. Bake in the over for 20 minutes or until the chocolate has just set in the centre.