Preheat the oven to 210º C.
Combine the butter, oil, water, sugar, and salt in a medium-sized ovenproof bowl - I used a Pyrex bowl.
Put the bowl in the oven for around 15 minutes, or until the butter starts to brown just around the edges and is bubbling.
Carefully remove the bowl from oven, keep your over mitts on as it will be VERY hot. Quickly stir in the flour until it pulls away from the sides of the bowl and forms a ball.
Dump the dough into a 9-inch/23 cm tart tin with a removable base and start spreading it out with a spatula.
Allow the dough to cool enough so you can handle it and spread it out evenly across the base and up the sides. Use a fork to gently press the dough against the sides to reinforce it.
Keep a small piece of dough aside for patching any cracks.
Prick the dough all over with a fork, then bake in the oven for 15 minutes until golden brown. Allow to cool completely before filling with the chocolate mocha ganache.