Chop the onion finely and slice the bacon thinly.

Sauté the onion and bacon in a pan without oil, as bacon releases its own fat.

Peel the boiled potatoes and place them in a bowl. Cut them roughly with a spoon.

Add milk to the potatoes and mash them until smooth. Adjust the milk quantity based on desired consistency.

Transfer the mashed potatoes to a microwave-safe dish.

Spread tomato sauce generously over the mashed potatoes.

Layer the sautéed onion and bacon on top of the tomato sauce.

Top with a generous amount of mozzarella cheese. Optionally, sprinkle parsley flakes.