- 3 pounds new potatoes
- 4 teaspoons salt
- 3 tablespoons unsalted butter
- 2 cups thinly sliced yellow onions
- 1 tablespoon minced garlic
- 1/2 cup minced green onions
- 1 cup shredded white cheddar
- 1 cup shredded Swiss cheese
- 1/2 teaspoon freshly ground white pepper
- 2 cups heavy cream
Preheat the oven to 350º F.
Place the potatoes in a large saucepan and add enough water to cover them. Season with 2 teaspoons of the salt. Bring the potatoes to a boil and then reduce the heat to a simmer and cook until the potatoes are tender, about 20 minutes. Drain and set aside to cool.
In a non-stick skillet, heat the butter and onions and add 1 teaspoon of salt. Cook over medium-high heat, stirring until the onions are golden brown and caramelized, about 10 to 15 minutes. Add the garlic and the minced green onions and cook for 2 or 3 minutes longer.
Slice the potatoes 1/8-inch thick. In a casserole dish, alternate the potatoes, onions, and cheeses in two layers and season with the remaining salt and pepper. Pour the heavy cream over the gratin and cover with aluminum foil.
Bake for 30 minutes, uncover and bake until the top is golden brown, another 15 or 20 minutes. Allow the gratin to cool slightly before serving.