Heat a large skillet over medium heat. Add diced ham and cook for 4–5 minutes, stirring occasionally, until golden brown on the edges.

Stir in sliced potatoes and chopped onion. Cover and cook for 15–20 minutes, stirring occasionally, until potatoes are tender and onions are soft.

In a small saucepan, melt butter over medium heat. Stir in milk and heat for 2–3 minutes until warm but not boiling.

Pour the warm butter-milk mixture over the potato and ham mixture. Sprinkle cheddar cheese on top. Cover and cook for 5 more minutes until cheese is melted and gooey.

Add salt and freshly ground black pepper to taste. Serve hot straight from the skillet.