Preheat the oven to 210ºC (190ºC fan-forced).
In a medium size oven-proof bowl or dish, add the butter, oil, water, and salt; place in the oven for 15 minutes.
Carefully remove the bowl from the oven with oven mitts. It will be sizzling and splattering, so be very careful! Place the bowl onto the kitchen bench with a tea towel or pot holder underneath.
In a separate bowl, mix the flour, parmesan cheese, and black pepper.
Slowly stir the flour mixture into the hot butter. It is important to still be cautious of the hot butter, it may still pop when you add the first bit of flour. Also, remember that the bowl is very hot, so wearing oven mitts while stirring is ideal. Stir the mixture until combined. Let it sit and cool for 5 minutes.
Once the dough is cool enough to handle, divide it evenly into mini tart moulds. With your fingers, press the dough flat and up the sides of the moulds. Prick the shell with a fork.
Place tart shells it into the freezer while you are making the next one, and then repeat. Place the last tart shell into the freezer and let cool for 5 minutes.
Place the tart shells onto a baking sheet and place in the oven on the middle rack. Bake for 15 minutes. Remove from the oven and place on a wire rack to cool before filling.