Bring a large pan of salted water to the boil, add the cabbage and boil for one minute. Remove with a slotted spoon, drain well and set aside.
Add the potato to the same pan of boiling salted water, cook for ten minutes or until very tender. Drain well.
Melt the butter in a large frying pan over a low-medium heat. Add the cabbage, potato, leeks and sage and fry gently.
Meanwhile, bring a large pan of water to the boil, add the pasta and cook according to packet instructions. Drain well and add to the frying pan with the cabbage and potatoes. Cook for three minutes, stirring gently.
Remove from the heat, stir in the bitto or parmesan and the fontina. Season, to taste, with salt and freshly ground black pepper and serve.
