Slice the sweet potatoes into ½-inch rounds. Steam for 8–10 minutes or until just beginning to become tender but still firm enough to hold their shape. Lightly dust with chili powder or your favorite spices before grilling, I find sweet and spicy go incredibly well together. Transfer carefully to a hot grill and cook for 3–4 minutes per side or until nicely charred and tender all the way through. Garnish with fresh chives or parsley before serving.