Asiago, Potato, and Bacon Gratin

from Cooking Light

1 1/2 lbs. Yukon gold potatoes,cut into 1/4" slices
1 t salt, divided
2 T shallots
1/4 c flour
2 c low-fat milk, divided
3/4 c grated Asiago cheese
1/4 c chopped fresh chives
1/4 t ground black pepper
4 bacon slices, cooked and crumbled
1/4 c grated Parmesan cheese

Preheat oven to 350°. Place potatoes in a large saucepan; cover with water. Bring to a boil. Reduce heat; simmer 5 minutes or until potatoes are almost tender. Drain. Sprinkle potatoes evenly with 1/4 teaspoon salt; set aside and keep warm. Heat a medium saucepan coated with cooking spray over medium heat. Add shallots; cook 2 minutes or until tender, stirring frequently. Sprinkle flour over shallots. Gradually add 1/2 cup milk, stirring with a whisk until well blended. Gradually add remaining 1 1/2 cups milk, stirring with a whisk. Cook over medium heat 9 minutes or until thick, stirring frequently. Remove from heat; stir in 3/4 teaspoon salt, Asiago, chives, pepper, and bacon.
Arrange half of potato slices in an 8-inch square baking dish coated with cooking spray. Pour half of cheese sauce over potato slices. Top with remaining potato slices and cheese sauce; sprinkle with Parmesan. Bake at 350° for 35 minutes or until cheese is bubbly and lightly browned.