Heat oil in a casserole, add onion and cook over medium heat until soft (8-10 minutes), add garlic and anchovies, cook until anchovies dissolve (1-2 minutes). Add stock and lamb, bring to a simmer, skimming scum, reduce heat to low, cover, and simmer, stirring occasionally, until lamb is tender (2½ hours). Add peas and oregano, simmer until tender (4-5 minutes). Stir in endive, cook until wilted (1 minute). Serve immediately with bread.