Pre-heat the oven to 190°C 375°F gas mark 5.
Roll out the pastry in a circle and use to line an ovenproof 20cm (8") flan tin or dish. Chill.
Wash the spinach well and trim off any coarse stalks. Drain. Melt the butter in a pan and cook the spring onions and the garlic until soft but not brown. Add the washed spinach in batches to the pan, tossing in the butter. When the spinach has all collapsed remove the pan from the heat. Add the parsley.
In a basin beat together the eggs, cream and milk and season with salt and pepper.
Lay the spinach mixture in the pastry case. Crumble the feta cheese over the spinach and pour over the egg and cream mixture.
Bake in the middle of a pre-heated oven for 25-30 minutes until the filling is set and a pale golden brown.