Turn the slow cooker on. Heat a large frying pan with 1 tbsp of the oil. Brown the sausages and pork steaks on all sides and remove.
Add the remaining oil and onions and saute for 5 minutes. Sprinkle in the flour and saute another minute. Add the mustard, cumin, some seasoning and the cider. Stir well and pour into the slow cooker along with the meat.
Cook for 4 hours on high heat or 8 hours on low heat. During the last 30 minutes of cooking, add the leeks and place on top of the meat. Serve as a stew or with mash and fresh chopped flat leaf parsley.