potato spinach gratin

3 shallots, thinly sliced
1 Tablespoon butter
2 packages [10 ounces each] frozen chopped spinach thawed and squeezed dry
1 teaspoon salt, divided
1/2 teaspoon salt divided
1/2 teaspoon peppers, divided
1/8 teaspoon ground nutmeg
3 pounds medium potatoes [about 9 medium] peeled and thinly sliced
1 cup shredded gruyere or swiss cheese
1 Tablespoon corn starch
1 1/2 cups 2% milk
1 cup heavy whipping cream

In a large skillet, saute shallots in butter until tender. Add the spinach, 1/2 teaspoon salt, 1/4 teaspoon pepper and nutmeg.

In a greased 3 quart baking dish, layer half of the potatoes, 1/3 cup cheese and half of spinach mixture. Repeat layers. Top with remaining cheese

In a small bowl, combine the cornstarch, milk, cream and remaining salt and pepper until smooth. Pour the milk mixture over cheese.

Cover and bake 350 for 1 hour. Uncover; bake 15-20 longer until potatoes are tender.