Lightly score the duck skin into diamonds and rub all over with the salt and half the garlic.Place the breasts skin side down in a heavy bottomed frying pan over a moderately low heat. The fat will gradually melt enough for you to increase the heat and turn the breasts over. Seal their underside and continue to fry gently on both sides until cooked to your liking.
Meanwhile heat 2 tbsps olive oil in a saucepan and saute the bacon until it begins to colour and no longer releases any water. Add the remaining garlic and the spring onions and continue to fry gently for 2 minutes. Stir in the peas and the lettuce plus 140 ml of the stock. Simmer for a further 5 minutes.
Once the duck breasts are nicely browned but still rare ad juicy remove from the pan and keep warm . Pour off the excess duck fat and deglaze the pan with the remaining stock. Reduce, then stir into the peas.
Quickly stir the butter into the peas and remove from the heat. Add the mint and adjust the seasoning to taste. Serve immediately with the duck breasts and some potatoes.