1. Preheat your oven to 180°C/Fan 160°C/Gas 4.
2. To make the pastry sift the plain flour and icing sugar into a large mixing bowl, along with your butter. Work the mixture through your hands to turn into a crumb. It should fall off your hands easily.
3. When the dough's looking ready, add 1 tsp water and 3 egg yolks and bring all the ingredients together. It might be sticky to start with, but keep going until you get a nice ball of dough. Chill for 25 mins.
4. After 25 mins your dough should be ready to go. Sprinkle some flour onto your work surface and rolling pin so it doesn’t stick and dust a little on top of your dough. Roll your dough. Make sure to pick it up and twist it, while dusting on more flour, so the dough is evenly rolled. Make sure not to work it too much otherwise it becomes too hot.
5. Line your baking dish with greaseproof paper and brush with a little butter. Slide the pastry in, tucking the sides over the dish and push it into the corners so your dish is completely covered.
6. Prick the pastry with a knife to ensure it can be heated through. You will be blind baking, so pour black beans over the pastry and spread equally and into the corners. This will help ensure the pastry cooks evenly and also helps weigh it down so it doesn’t get any lumps in it.
7. Pop the pastry into the oven for 15 mins. Take out, remove the beans and pop back in the oven for a further 10 mins.
8. While that’s cooking, make your caramel. Get a pan hot. Add the caster sugar and swirl in the pan until it become liquids, then add 300ml double cream and a shot of espresso, until it is all incorporated together. Take off the heat and let it cool down.
9. While the caramel is cooling, make your ganache. Get a heavy based pan hot and pour in 500ml double cream. Bring to a simmer and add the dark and milk chocolate. Once all the chocolate is in the pan, take off the heat and mix it all together with a wooden spoon, until liquified. Leave to the side to cool.
10. By now your pastry should be ready. Remove from the oven and trim the sides. Leave to cool.
11. Once the pastry is completely cooled, pour the caramel over the base. Pop aside to allow the caramel to set. Once the caramel is nice and firm, you can spread the ganache evenly on top. Pop your Millionaire Mocha Tart in the fridge. Leave it to set overnight.
12. When your tart has fully cooled, take out and trim off the rest of the crust and then dust with sieved cocoa powder and enjoy!