Preheat oven to 350 degrees (if making the same day).
In an enamel-coated cast iron pan add the olive oil and heat over medium-high heat. Add the diced onions and season with a pinch of coarse sea salt and ground black pepper and cook until onions begin to soften.
Push the cooked onions to one side of the pan and on the empty side of the pan add the uncased breakfast sausage meat to the pan, reduce to medium heat, and using two forks, break apart the breakfast sausage meat into small pieces. Cook until the sausage loses its pink color. Once the sausage is cooked, combine the sausage and the onions.
Add the diced uncooked potatoes. Season with coarse sea salt, ground black pepper, and smoked paprika. Stir well to combine.
*At this point, the potatoes can be cooled, covered and refrigerated overnight*
When ready to bake, place potatoes in a preheated 350-degree oven and cook covered for 30 minutes or until potatoes are tender. Remove cover and continue baking for another 15 minutes until potatoes are golden brown.
Remove from oven and top with sliced green onions.
Serve immediately.