Make the pastry by the usual method, then halve it, form each half into a disc, wrap in plastic wrap, and leave in the refrigerator for 20 minutes.
Preheat the oven to 400 degrees.
Meanwhile, peel and dice the potatoes, put them in a saucepan with plenty of cold water, and bring to the boil. Boil gently for 5-10 minutes, or until the cubes are cooked but still retain their shape. Drain and leave to cool.
In a large bowl, combine the green onions, cheese, slightly cooled potato, and parsley. Bind with the creme fraiche and season with salt and pepper. Roll out one of the pastry discs, cut 8 rough circles slightly larger than the indents, and push 4 into the first tray to make the bases. Fill each with an eighth of the mixture and put the remaining 4 circles on as lids. Seal the pie edges with the back of a knife, making a little hole in each one. Repeat for the second tray with the other disc and the remaining half of the filling.
Cook for 20 minutes, by which time the pastry should be firm, beginning to turn gold, but still pale, and let the pies stand a little out of the oven in their trays before easing them out of the molds.
Recipe courtesy of Nigella Lawson's How to Be a Domestic Goddess (Hyperion, 2001)