Chipotle Sweet Potato Gratin

In 4-quart Dutch oven, place sweet potatoes and just enough water to cover potatoes. Heat to boiling; reduce heat to medium-low. Cover; cook 20 minutes or until almost tender. Drain; cool slightly. Peel potatoes; cut crosswise into 1/2-inch slices.

Heat oven to 350°F. Spray 2-quart oval gratin dish or 3-quart casserole with cooking spray. Arrange potato slices overlapping in gratin dish.

In 3-quart saucepan, melt butter over medium heat. Cook onion and garlic in butter, stirring frequently, until tender. Sprinkle flour over onion mixture; cook 1 minute, stirring constantly. Gradually add half-and-half, stirring constantly until thickened and bubbly. Stir in salt, cumin and pepper. Add cheese and chipotle chiles; stir until cheese is melted. Pour cheese sauce over potatoes.

Bake uncovered 45 minutes or until lightly browned and bubbly. Let stand 15 minutes before serving.