I never put the outside leaves of a cos lettuce in a salad, because they are too tough. I save them for a delicious risotto, or for this equally delicious pasta sauce.
Heat half the oil, the shallots, garlic and chilli in a large frying-pan. Add 2tablespoons of hot water and 2 pinches of salt and cook for 7 minutes, shaking the pan very frequently.
Mix in the cos lettuce and cook until it becomes limp. Now stir in the passata and co