How to cook
Sift the flour in a bowl and make a hole in the middle. Add the salt, egg yolk, and butter. The butter should be at room temperature, but not too soft.
Mix with your hands until you get a crumbly dough. Add some water if needed to bring all the ingredients together, and knead until you have a hard dough, but not for too long, so the butter doesn't melt.
Wrap it in cling film and let it rest in the fridge for 30 minutes. In the meantime clean the mushrooms and spinach. Clean the onions and chop finely.
Pour some olive oil in a pan and saute the spring onions, then add the spinach and cook it until it softens. Remove the spinach mix from the pan and saute the bacon. Remove the bacon and place it on a piece of kitchen paper to absorb the excess oil.
Melt the butter in a pan and saute the mushrooms cut in big pieces. In a bowl mix the sour cream, pepper, spinach and stir. Take the dough out of the fridge and roll it out, so its diameter is slightly bigger than the tart pan you will use.
Grease the pan, place the dough on the bottom and the sides of the tray.
Add the spinach mix, flatten it gently, and add the mushrooms and bacon.
Grate the cheeses and sprinkle on top.
Whisk the eggs in a bowl, add the milk and pour the mix over the quiche.
Bake in a preheated oven to 338°F (170 degrees) for 50 minutes, until it turns golden brown.
Let the quiche cool, slice it and serve.