Remove sausage from casing, and cook over medium heat in a medium skillet to render some of the fat. Remove partially cooked sausage to a small bowl, and cook onion in the sausage drippings until translucent. Add the sausage back to the pan.
Meanwhile, if using frozen diced sweet potatoes, microwave for 1 minute to soften. Add to pan with sausage and onions.
Fry or poach 4 eggs (2 per person), and make toast. When the sweet potato is heated through and a little crispy on the outside and sausage is fully cooked, divide the hash between two plates and place 2 eggs over each plate of hash. Serve with toast.