Peel the potatoes and put in a large pan with water along with the sausages. Cook until the potatoes are tender enough to be mashed.

Drain and mash the potatoes. Set aside. Chop the sausages and set aside.

In a large pan, add the butter, ½ grated onion, mashed potatoes, and milk. Mix until it becomes a puree. Season with salt and pepper. Set aside.

In a large pan, put the oil, chopped onion, green chili and mix until the onion is transparent.

Add the chopped sausage, tomatoes, and salt. Cook until the tomatoes are soft and become a sauce. Sprinkle in the parsley and green onions. Mix gently. Set aside.

Preheat the oven to 200ºC (400ºF).

In a large, oven-safe casserole dish, smooth a layer of half the potato puree, a layer sausage sauce, mozzarella, then the remaining potato puree.

Sprinkle the top with parmesan cheese and chopped parsley.

Bake for 35 minutes or until the cheese is melted and the top layer is turning it is golden.