First make the pastry: In a food processor, blend the butter, flour and salt to for a mixture like breadcrumbs. Add about 50ml of cold water and whizz. Take the mixture out of the food processor and form a ball but take care not to handle too much or it will be too hard. Wrap the ball well in cling film and put in the back of the fridge to rest for 30 to 50 minutes.
Preheat oven to 200 C / Gas 6 and lightly grease the quiche tins (15cm diameter). Roll the pastry out on a lightly floured surface to a thickness of about 5mm. Using the tins as a guide cut circles in pastry about a centimetre wider than the tins depending on their depth. Line tins with the pastry being generous, bearing in mind the pasrty will shrink slightly while cooking. Prick bottom with a fork.
Bake blind for 10 to 15 minutes. Use baking beans if you have them.
For the filling: Meanwhile separate the egg whites and yolks and beat the whites to form peaks but not too stiff. In a bowl beat the yolks with the creme fraiche and milk and season to taste. Fold the whites into the mixture.
Put 3 or 4 tomatoes into each pastry case and cover the bottom with chorizo and green pepper. Pour the egg mixture over the top as high as you dare or a thicker quiche.
Return to oven for 25 to 35 minutes until top is starting to brown and middle is set. If the top browns before the middle is set, put some kitchen foil over the top.
If you don't have lots of time, use ready made shortcrust pastry.