Crempog Las is a Welsh omelette, which isn't really an omelette, but more of an eggy pancake.
The basic recipe is;
8 oz plain flour
4 tablespoons of milk
which is mixed together to form a stiff batter, poured into a frying pan, and cooked as you would a normal omelette. (I have seen some recipes that insist that you should separate the egg yolks from the whites and add them to the mixture at different stages, but I really wouldn't bother. Life is to short to stuff a mushroom and all that. I simply throw the whole lot into a food processor and press play.)
You will need to add some flavour to this basic mixture. Some pepper and salt would be a good idea, and chopped parsley is standard, although exactly how much is up to you; the suggested quantities vary from a teaspoon to a whole four whole tablespoons worth. Some people would leave it at that, perhaps adding a dash of nutmeg, although it would be normal to add some chopped leeks or even spring onions or shallots according to taste.