In a cast iron skillet, heat the oil on medium and add the onion. Cook for 3-4 minutes until tender and starting to be translucent.
Remove the sausage from their casing and add them to the pan with the onion. Using a spoon or spatula, gently break up the sausage meat and cook gently until sausage is browned. If you want to add the crushed chillies, add them in at this point.
Once the sausage is cooked, remove the onion and sausage mixture from the pan and transfer to a plate or bowl for later use.
In the same cast iron skillet, add the diced sweet potato, season with sea salt and cook for 5 to 7 minutes until potatoes soften and edge begin to brown. If you find the potatoes are sticking to pan just a little drizzle of oil.
Once the potatoes have soften, return the sausage mixture to the pan and stir to combine with the potatoes.
Using a spoon, make four wells in the potato mixture and crack an egg into each.
Transfer the skillet to the oven for 10-15 minutes until eggs are cooked to your liking.
Remove from the heat and sprinkle with chopped scallions.