Start by bringing a large pot of salted water to a boil. Add 1.5 pounds of peeled potatoes and cook for 10–15 minutes until tender. Drain the potatoes thoroughly and mash them in a large bowl with half a cup of butter, seasoning with salt and pepper to taste.

In a separate pot, add 5 eggs and cover them with cold water. Bring the water to a rolling boil, then reduce heat and let simmer for 8–10 minutes. Transfer the eggs to an ice bath to cool for easier peeling. Peel and halve the eggs lengthwise.

While the eggs cool, wash 4 large leeks thoroughly to remove any sand. Boil the leeks in salted water for 4–5 minutes until tender. Drain and mix the leeks into the mashed potato mixture.

In a medium saucepan, melt the remaining 1/4 cup of butter. Whisk in 2 tablespoons of flour, cooking for about 1–2 minutes. Gradually add in 2 cups of warm milk, whisking constantly until thickened. Stir in 1/2 teaspoon of nutmeg and 6 ounces of grated sharp Cheddar cheese until creamy.

Preheat your oven to 375°F (190°C). In a greased baking dish, layer the creamy mashed potato and leek mixture. Arrange the halved eggs cut-side up on top. Pour the cheese sauce over the eggs and sprinkle the remaining cheese on top.

Bake for 20–25 minutes or until the top is bubbling and golden brown.