Preheat oven to 350 degrees F. Grease a 12-cup standard muffin pan.
Cook bacon in skillet until crispy. Remove to paper towel lined plate. Reserve 1 tablespoon bacon fat in skillet, drain off excess.
Cook sweet potato in skillet over medium low heat until wilted (about 5 minutes). Stir in green onions. Turn off heat and set aside. (if using regular onions instead of green onions, cook them with the sweet potatoes.)
Whisk together eggs, half and half, salt and pepper in a bowl.
Fill each cup with evenly with the sweet potato, green onion, bacon and cheese. Pour the egg mixture evenly over the top. (Sometimes you need to spoon a little egg from one cup to another to even them out.)
Bake for 25-30 minutes. (Will puff up a lot while baking, then will settle down once cool.) Let cool about 5 minutes in pan. Loosen the edges with a thin knife to remove.
Store in refrigerator for up to 3 days or wrap individually in plastic wrap and place in a freezer bag or container. Can reheat in warm oven or microwave.
Nutrition (approx. data estimated via online nutritional calculator.)