Adapted from Cooking Light, Dec. 2012 – Delicious!
2 medium baking potatoes, peeled and cut into 1/4-inch-thick slices
2 medium sweet potatoes, peeled and cut into ¼-inch-thick slices
broth or water, for cooking potatoes
2 Tbs. canola oil
3 Tbs. all-purpose flour
2 cloves garlic, minced
1½ cups 2% milk
2 fresh thyme sprigs plus 1 ½ tsp. chopped fresh thyme
¾ tsp. kosher salt, divided use
¼ tsp. freshly ground black pepper
¾ cup shredded Gruyere cheese
¼ cup freshly shredded parmesan
Preheat oven to 350 degrees. Place potatoes in a large stockpot and cover with broth or water. Bring mixture to a boil; cook for 4 minutes. Remove from heat. Carefully remove potatoes from pot using a slotted spoon, reserving cooking liquid. Arrange potato slices in a single layer on a jelly-roll pan; set aside. Reserve 1 cup cooking liquid.
Heat a medium saucepan over medium heat. Add oil to pan; sprinkle flour over oil; cook 1 minute, stirring constantly with a whisk. Add garlic; cook 1 minute, stirring often. Combine milk and reserved 1 cup cooking liquid. Gradually pour milk mixture into flour mixture in pan, whisking constantly. Add thyme sprigs to pan; bring mixture to a boil; cook 3-4 minutes or until slightly thickened, stirring frequently. Remove from heat; strain. Stir ½ tsp. salt, pepper and Gruyere cheese into sauce.
Spread ½ cup prepared sauce over bottom of a broiler-safe 2 quart ceramic baking dish coated with cooking spray. Alternate baking potato and sweet potato slices in shingle-like fashion across the bottom of the baking dish. Sprinkle evenly with remaining ¼ tsp. salt and chopped thyme; pour remaining sauce over potato mixture. Sprinkle with parmesan cheese; bake at 325 degrees F. for 45-50 minutes, or until potatoes are fork-tender. Remove gratin from oven; preheat broiler to high. Place gratin under broiler and broil for 2-3 minutes or until nicely browned.
Now You’re Cookin’,