Scalloped Orange and White Potatoes

1 tablespoon bacon drippings or vegetable oil
2 large whole garlic cloves, finely chopped
1½ teaspoons finely chopped fresh lemon thyme or 1 teaspoon dried leaf thyme, crumbled
2 tablespoons all-purpose flour
2 cups light cream or half-and-half
1 teaspoon salt
½ teaspoon black pepper
4 large fresh bay leaves, bruised
3 medium baking potatoes (about 1½ pounds), peeled and thinly sliced
1 large sweet potato (about 1 pound), peeled and thinly sliced
2 tablespoons butter, cut into small dice

This is a great make-ahead, so it’s ideal for a dinner party. Serve with baked ham or any roasted meat or fowl.

Preheat the oven to 425° F. Spritz a shallow 2-quart casserole or gratin dish with nonstick cooking spray and set aside.
Heat the bacon drippings in a small, heavy saucepan over moderate heat for 1 minute, add the garlic and lemon thyme, and cook, stirring often, for 3 to 5 minutes or just until the garlic softens. Blend in the flour and cook and stir 1 minute more. Whisking hard, add the cream, salt, and pepper. Drop in the bay leaves and cook, whisking constantly, for 3 to 5 minutes or until the sauce is thickened and smooth.
Place the baking and sweet potatoes in the casserole and toss well to mix. Pour in the hot sauce and push the bay leaves down into the potatoes, distributing them evenly. Shake the casserole gently to level the sauce and potatoes, then dot with butter.
Slide the casserole onto the middle oven shelf and bake uncovered for about 40 minutes or until the potatoes are crusty-brown on top and tender underneath.
Remove the casserole from the oven, discard the bay leaves, and serve.