Preheat oven to 375°F (190°C).
In a large skillet over medium heat, cook the sausage and onion until the sausage is browned and the onion is translucent.

In a large mixing bowl, combine the cooked sausage and onion with the diced potatoes, 1 cup of cheddar cheese, milk, sour cream, melted butter, paprika, salt, and pepper.

Transfer the mixture into a greased baking dish. Sprinkle the remaining cup of cheddar cheese on top.
Bake for 60 minutes, or until the potatoes are tender and the top is golden and bubbly.
Garnish with chopped parsley before serving