Blood sausage — black pudding in Britain, morcilla in Spain, boudin noir in France — is a sausage built around fresh animal blood, usually pig's, set with a filler of grain, onion and cubes of fat and seasoned with warm spices. Cooked once in the making, then sliced and fried or grilled, it is dark to near-black, dense and crumbly to soft, and tastes deeply savoury, rich and faintly mineral from its iron-laden blood.