Preheat the oven to 180C/355F (160C/320F fan assisted).
Spray a 12-hole nonstick muffin tray with oil.
Once you've cut your filo pastry into quarters, it's a good idea to keep all the sheets under a very slightly damp tea towel so that they don't dry out.
Line each hole of the muffin tray with a filo square, pushing in firmly with a few corners peeking out at the top. Spray the inside of each pastry cup with oil.
Repeat the process until you have three layers of pastry in each hole, finishing with a spray of oil.
Pour equally into the pastry cases.
Put a few pieces of spinach, ham, mushrooms and/or tomato into each case. Don't overfill the cases. In a jug or bowl, whisk together the eggs, milk and a pinch of salt and pepper.
Pour the egg mixture evenly into the pastry cases, taking care not to overfill them.
Add a pinch of cheese to the of each quiche.
Sprinkle on a little freshly chopped parsley.
Place the muffin tray into the centre of the oven and bake for 20-25 minutes until the filling is risen and set and the edges of the pastry are golden.
Allow the quiches to cool a little before lifting from the tin.
Make sure to check that your quiches are cooked all the way through. A skewer should come out clean and they should feel firm when pressed, both on top and underneath.If they look like they are browning too quickly on top, cover loosely with foil to allow the filling time to cook.If you wish to store them for later once cooked and cooled, place in a single layer in a sealed container and place in the fridge. They should keep well for a day or two.