Translated from page 220 of Hanna Winsnes cook book:
As the blood of mutton and lamb has a stronger flavour than beef or veal blood, it is normally not used for yourself, but as black pudding or blood pancake for the servants.
Although lamb heads are the best, sheep heads can also be used, when they are not from too old sheep. They are scolded and split, the brain is removed, and then they are boiled in a little water, with a little salt. When they are boiled they are sprinkled with breadcrumbs, and browned in butter. An oblong pot with a slightly deep base is more suitable for this, then a frying pan, as they can fit inside better. A tertepanne (an old designed oven pot with lid and legs) is the best. With this (the dish) you can make red sauce, like for soup meat,or you can simply use the brown butter.
Read about Hanna Winsnes and the First Norwegian Cook Book.