Preheat your oven to 200°C.

Peel the potatoes and cut them into chunks. Boil them in salted water until they are parboiled (partially cooked but still firm), about 7-10 minutes. Drain well.

While the potatoes boil, slice the sausages into rounds.

In a large oven-safe pan (or transfer later to a baking dish), melt the butter over medium heat. Add the sliced sausages and pan-fry until they are slightly golden and released some flavor.

Add the parboiled potato chunks to the pan with the sausages. (If using, add sliced onion and cook until softened, then add minced garlic and cook for 30 seconds.) Stir to coat potatoes and sausages in the butter and pan drippings. Cook for a few minutes until potatoes start to get a little color.

In a small bowl, mix together the mayonnaise, ketchup, sour cream, salt, and pepper.

Pour the sauce mixture over the potato and sausage mixture in the pan. Stir gently to combine.

Sprinkle the grated cheese evenly over the top.

Transfer the pan (or baking dish) to the preheated oven.

Bake for 15-20 minutes, or until the cheese is melted and bubbly and the dish is heated through.

Serve hot, optionally garnished with fresh herbs.