Keep the sweetbread in cold water for one hour, clean it, poach it in hot salted water for five minutes and let it get cold.
Put in a saucepan à layer of carrots, onions, bits of bacon and bones; put the sweetbread on it, add salt and pepper, cook twenty minutes on a moderate fire, cover with oiled paper and finish cooking in the oven. Baste often. The sweetbread should be nicely brown. Serve on a purée of sorrel. 1