Ingredients

Unsalted butter, for baking dish

4 large sweet potatoes (about 4 pounds), peeled and thinly sliced into rounds

Coarse salt and freshly ground pepper

1 1/2 cups grated Chihuahua or Monterey Jack cheese (6 ounces)

1 1/2 cups Cotija or French feta cheese, crumbled (6 ounces)

1 small onion, thinly sliced

1 teaspoon finely chopped canned chipotle chile in adobo (optional)

1/4 cup plus 2 tablespoons homemade or low-sodium store-bought chicken stock, or water

1/4 cup finely chopped fresh cilantro leaves

1 cup crushed tortilla chips

Lime wedges, for garnish

Mexican crema or sour cream, for garnish (optional)

Preparation

Preheat oven to 350 degrees. Butter a 9-by-13- inch baking dish; set aside. Toss potatoes with 1 1/2 teaspoons salt and 1/4 teaspoon pepper. Arrange half of potatoes in buttered dish, overlapping slices. Sprinkle with half of each cheese. Top with onion.

Stir chipotle (if desired) into stock; drizzle over onion. Sprinkle with half the cilantro. Top with remaining potatoes; sprinkle with remaining cheeses and cilantro. Scatter chips on top.

Cover with foil; bake 30 minutes. Remove foil; bake until very tender and top is well browned, about 30 minutes more. Let cool slightly before serving. Serve with limes, and with crema, if desired.