Heat a large skillet with a tight-fitting lid over medium heat. Add first 5 ingredients (sausage through crushed red pepper flakes); cook and stir for 10 minutes or until sausage is mostly cooked through.
Add the kale then reduce heat, cover and simmer for 10 minutes. In a large bowl smash the cooked sweet potatoes with a fork. Serve sausage and kale over a large spoonful of smashed sweet potatoes.