Heat oil in a large skillet over medium-high heat; add in the sausage meat with chili pepper flakes (if using) onions and garlic, stir with a wooden spoon breaking up the meat, cook until well browned (about 10-12 minutes) drain the fat, then add in about 1/4 cup Parmesan cheese; mix to combine.
Spread the mixture into the baking dish.
In a bowl mix the soup with evaporated milk, then pour over the sausage mixture in the baking dish.
Sprinkle grated cheddar cheese over the soup.
Top with the potato nuggets evenly over the cheese.
Sprinkle the top of the nuggets lightly with seasoned salt and black pepper, then sprinkle with Parmesan cheese to taste.
Bake uncovered for about 50-60 minutes, or until lightly browned.