In a large pot, brown the Italian sausage and onion. Drain any fat. Add garlic and red pepper flakes to the pot and cook for 1 minute.
Add chicken broth and the potatoes and cook over medium heat until the potatoes are almost cooked through, 10-15 minutes.
Stir-in kale and half-and-half. Simmer for about 10 minutes or until kale is soft and potatoes are fork tender. Season with salt and pepper. Serve immediately.