Put the split peas in a pan and cover them with cold water. Bring this to the boil very slowly, remove from the heat and leave to soak for 1 hour.
Then drain the peas and place them back in the saucepan together with the onion stuck with cloves, the mixed herbs and some salt. Cover again with cold water and simmer till tender (about 20 minutes). Then drain the peas again and rub them through a sieve into the top of a double saucepan (or a basin sitting over some simmering water); stir in the cream and butter, and leave it like this for about 20 minutes, stirring now and then until it becomes very thick.
Season with pepper and freshly grated nutmeg, and more salt if it needs it. Serve the puree piled on to a plate with the fried sausages on top.