Scalloped Potatoes

Preheat oven to 400°F. Lightly coat an 11- x 7-inch baking dish with cooking spray.

Melt 4 tablespoons of the butter in a medium saucepan over medium. Add flour, and cook, stirring constantly with a wooden spoon, until a paste forms and bubbles, 1 to 2 minutes (do not let it brown). Whisk in milk, and bring to a boil over medium, whisking often. Reduce heat to medium-low; whisk in nutmeg and 1 1/2 teaspoons of the salt. Cook, whisking occasionally, until thickened, 2 to 3 minutes. Remove from heat, and set aside.

Heat remaining 2 tablespoons butter in a large nonstick skillet over medium. Add onion, thyme, and remaining 1/2 teaspoon salt; cook, stirring occasionally, until softened, about 15 minutes. Remove from heat.

Add one-third of the potatoes to the bottom of the prepared baking dish in a single layer. Top with half of the onion mixture (about 2/3 cup) and one-third of the cream sauce (about 2/3 cup). Add one-third of the potatoes, remaining onion mixture, and one-third of the cream sauce. Add remaining potatoes, and top with remaining cream sauce.

Cover, and bake in preheated oven for 30 minutes. Uncover, and bake until bubbly and golden brown, 20 to 25 minutes. Remove from oven, and let stand 10 minutes. Serve.