Clean and fillet the herring. Mince the fillets, anchovies, roast lamb and onions in a mincer of a food processor.
Melt the butter in a saucepan, add the meat mixture and bring to the boil. Add a little meat juice or consommé until the mixture becomes porridge-like in consistency. Add tomato sauce or puree and pepper to taste. Add the mustard and cream.
Simmer the lamb for 30 minutes, stirring occasionally to prevent sticking. Serve steaming hot with pickled cucumbers, pickled beetroots and soured cream. The traditional drink, Ryyppy is served ice cold as an accompaniment to the meal.