Spicy Sausage, Potato & Kale Soup

spicy italian sausage (I used chicken but pork is good too)

butter or olive oil

large onion, chopped

garlic cloves, minced

salt, plus more to taste

freshly cracked black pepper, plus more to taste

crushed red pepper flakes, optional

large bunches of kale, stemmed and chopped, about 4 overflowing handfuls

freshly grated nutmeg

medium or 2 large russet baking potatoes, sliced

chicken broth or stock, 2 boxes

heavy cream