Cheese, mushroom and bacon tart

Forget sliced bread. The best food invention ever was ready-made pastry.
With its arrival, any random fridge/cupboard ingredients can be turned into PIE with minimum effort. Pies always look impressive (especially if made in my giant pie dish), go down well with guests and can be cooked in the oven -- all winning attributes in my book.
In terms of filling, pretty much anything goes -- this is an approximate breakdown of a pie (or, strictly speaking, a tart) I made this week for a games night, which reminds me of another pie bonus -- it can be eaten with your hands so is a good snack/buffet food.

Serves 4

1 pack shortcrust pastry
1 punnet of mushrooms
2 onions
150g stilton
150g cheddar
4 rashers of bacon
200g Greek yoghurt (you could also use single cream, sour cream or creme fraiche)
2 eggs
salt, pepper, herbs (I used rosemary and sage)

Preheat the oven to 200 degrees. Butter your pie dish and line it with pastry. Top with baking beans and bake for about 10 minutes.
Chop and fry the onions, bacon and mushrooms until cooked. You could also add garlic, celery, spinach -- anything you like really.
Beat together the eggs with the yoghurt and add the seasoning.
Layer the onions, bacon and mushrooms over the pastry (remove the baking beans first!).
Scatter over the grated cheese. Top with the yoghurt and egg mixture.
Return to the oven for another 20 minutes or so until cooked and browned on top.
Serve with salad or some form of cooked greens.