In a large saucepan heat a few tablespoons of olive oil with a clove of garlic – do not peel it - and some leaves of sage. When the garlic has flavoured the olive oil and the sage leaves are crispy, remove the garlic and pour in the beans with some spoonfuls of their cooking water. Add a few tablespoons of tomato sauce to redden the beans. Season with salt and pepper.
Bring to a simmer and let it cook for half an hour or so. Now add the peeled sausages and simmer gently until the sausages are completely cooked through.
Serve hot with some toasted slices of Tuscan bread to dip into the sauce and eat the sausages.