Wash the kale thoroughly and blanch in boiling water for about 1 minute. Pour onto a sieve, drain and allow to cool slightly. Peel, wash, halve and slice the potatoes.
Peel and chop the onion. Clean, wash and cut the bell peppers into strips. Finely chop the kale. Heat oil in a pot. Steam potatoes, onion and bell peppers for about 2 minutes. Add kale.
Add stock, bring to the boil, cover and cook for about 15 minutes. Cut the sausages into thick slices and add to the cabbage about 3 minutes before the end of the cooking time. Season kale stew with salt, pepper and mustard.