In a heavy 8 to 9 quart stockpot, heat the olive oil over high heat. Add the sausage and onion and saute for 2 minutes. Add the garlic, parsley and beans and cook for 2 minutes. Add the chicken stock and bring to a boil. Stir in the bay leaves, thyme, salt, pepper flakes, and black pepper. Reduce the heat to medium and simmer, uncovered, until the beans are tender, about 1 1/2 hours. Add the potatoes and kale. Continue to simmer for 30 minutes, or until the potatoes are tender. Skim the fat from the top with a large spoon. Pour the soup into individual soup bowls and stir 1 tablespoon of mint into each bowl. Allow the mint to steep and infuse its flavor for 1 to 2 minutes. Serve with crusty Portuguese or French Bread.