1 pound green beans, rinsed, ends trimmed, and cut into 2-inch pieces
8 ounces cooked or smoked ham, cut into 1/2-inch pieces
1 1/2 pounds white thin-skinned potatoes, peeled and sliced into 1/8-inch-thick rounds
4 large eggs
1 1/2 cups milk (whole or 2%)
1 tablespoon lemon juice
1/2 teaspoon salt
1/4 teaspoon pepper
1 cup grated Swiss cheese (about 2 1/2 oz.)
How to Make It
In a 4- to 5-quart pan over high heat, bring about 2 quarts water to a boil. Add green beans and cook until crisp-tender to bite, about 3 minutes. Drain.
In a lightly oiled 3-quart baking dish, arrange about a third of the ham, followed by a third of the beans and a third of the potatoes. Repeat to make two more layers.
In a bowl, beat eggs, milk, lemon juice, salt, and pepper just to blend. Pour over potatoes. Cover dish with foil.
Bake gratin in a 350° oven until potatoes are tender when pierced, about 45 minutes. Uncover, sprinkle cheese evenly over top, and continue to bake until cheese is browned and bubbling, about 25 minutes longer.