Drain the peas and put them in a pan with the onion, herbs and water. Bring to the boil, cover the pan and simmer until the peas are tender - about an hour. Check during the cooking, stir occasionally, and add a little more boiling water if the peas are drying out before they are cooked. Beat the peas well to make a smooth purée - or liquidise them - and beat in the egg and seasoning. The purée should resemble a thick paste.

Either turn the purée into a greased and floured pudding cloth, tie it securely and boil it (preferably in meat stock) for 1 hour or turn it into a shallow, greased ovenproof dish, level the surface and bake in the oven preheated to 180 ° C / 350 ° F / Gas 4 for 30 minutes.