If you want to make the dough yourself:
…Or you just use dough from the super market.
For the filling
Step 1: grease the form pan (Ø 28cm) and powder it with a bit of flour. Preheat the oven to 200° ( Circulating Air: 180°). Defrost the spinach.
Step 2: knead the flour with butter, salt and the egg. Powder your countertop with some flour. Roll out the dough until it‘s a bit larger than your form pan. Put the dough in the form pan and press it to the frame of the pan to create the rim. You can cut the rest of the dough that protrudes the form pan. Now put the dough in the preheatead oven for about 10 minutes.
Step 3: dice the onion and the feta cheese in cubes. Put the defreezed spinach in the form pan and put the onion and feta cubes on top. Mix the egg with cream, sour cream and the cheese. If you want you can flavour them with salt, pepper and nutmeg.
Now pour the mixture over the dough, the spinach and the onion/feta cubes. You still should see the rim of the dough. Place pine nuts on top. Now bake the quiche for another 30 minutes in the preheated oven.
Ready to eat!