Italian Bread and Cabbage Soup with Sage Butter

Name: Italian Bread and Cabbage Soup with Sage Butter
Ingredients: 3 quarts good-quality chicken or vegetable stock; 1 Savoy cabbage, stalks removed, outer leaves separated, washed and roughly chopped; 2 big handfuls cavolo nero and/or kale, stalks removed, leaves washed and roughly chopped; About 16 slices stale country-style or sourdough bread; 1 clove garlic, unpeeled, cut in 1/2; Olive oil; 12 to 14 slices pancetta or bacon; 1 (4-ounce) can anchovy fillets, in oil; 3 sprigs fresh rosemary, leaves picked; 7 ounces fontina cheese, grated; 5 ounces freshly grated Parmesan, plus a little for serving; Sea salt and freshly ground black pepper; Couple large knobs butter; Small bunch fresh sage, leaves picked