How to cook
Wash and dry the spinach and sorrel. Saute the leeks in the oil and add the chopped leafy greens.
Pour in about 1/2 cup (120 ml) and saute with the lid half closed until the liquid evaporates. Season with salt and black pepper to taste.
Lay out a sheet of puff pastry along the bottom of a baking tray.
Press strips of puff pastry along the edges of the tray, so the filling doesn't spill out.
Pour in the filling, smooth it out and arrange strips of puff pastry on top, pressing on them lightly.
Smear them with beaten egg yolk and put the spinach pie to bake in a moderately heated oven until ready.