Cut the potatoes into chunks - the exact size doesn’t matter, but try to cut them evenly. I left mine unpeeled. Once chopped, add them to a pan of water, and boil for around 15 minutes, or until completely soft.
Meanwhile, heat the oil in a large frying pan, and add the chopped leek and minced garlic. Cook over a medium heat for around 5 minutes, until soft and fragrant.
When the potatoes are cooked, mash them thoroughly, and add the butter, grated cheese, parsley, and cooked leeks. Mix thoroughly until the cheese and butter have melted through the hot potatoes. Season generously.
Heat the oven to 190°C (Gas Mark 5 / 375°F).
Cut the filo pastry into squares that measure approximately 3 inches (I was able to get 12 squares out of each sheet of pastry, so cut 48 squares altogether, which was enough for 24 homity pie bites).
Grease two cupcake trays with butter or oil, and press one square of filo into one of the cups. Spray the pastry lightly with oil, then place a second piece of pastry on top, at a different angle to the first. Gently press the pastry into the cup. Repeat with the other cups until all the pastry squares have been used up.
Divide the potato mixture between the pastry cups. Lift the corners of the pastry, and gently press them together on top of the filling to create a pocket. Spray once more with oil, then place in the oven and bake for around 25 minutes, until golden brown and crispy (check that they’re crispy underneath too!).