After Thanksgiving Turkey Shepherd's Pie

1. Generously butter a shallow 1-1/2-quart baking dish. 2. For the turkey and cranberry filling: Melt 1 tablespoon of the butter with the canola oil in a heavy, medium saucepan over medium heat. When hot, add the pearl onions and sauté, stirring frequently, until nicely browned and tender when pierced with a sharp knife, 4 to 5 minutes. Remove pearl onions from saucepan and set aside. 3. In the same saucepan over medium heat, melt the remain¬ing 2-1/2 tablespoons butter and, when hot, add the flour and whisk constantly until it turns medium brown, 2 to 3 minutes. Gradually add the chicken broth and bring to a gentle boil, whisking constantly until the sauce thickens enough to coat the back of a spoon. Stir in the wine, cranberries, orange zest, thyme, 1/2 teaspoon salt, and several grinds of pepper. Return the sautéed pearl onions to the pan. Cook for 1 minute more, and then remove from the heat and season with more salt if needed. 4. Either cut or tear the sliced turkey into strips about 3 inches long and 1/2 inch wide, and spread in the pre¬pared baking dish. Pour the sauce over the turkey and toss well to coat evenly. (The casserole can be prepared up to this point 2 hours ahead. Cool, cover, and refrigerate. Bring to room temperature 30 minutes before continuing with the recipe.) 5. Arrange a rack in the middle of the oven and preheat to 375 degrees. 6. For the mashed potato topping: Bring a large pot of water to a boil and add 1 tablespoon salt. Cook the potatoes until tender, about 15 minutes. Heat the half-and-half and butter in a small saucepan until warm and set aside. 7. When the potatoes are done, drain them in a colander and return to the pot. Mash with a potato masher. Stir in the half-and-half and butter. Season the potatoes with 1/2 teaspoon salt, or more if needed. With a rubber or metal spatula, spread the mashed potatoes evenly on top of the turkey in the baking dish. Make wavy patterns in the potatoes with the spatula. (The casserole can be prepared up to this point 30 minutes ahead. Leave, uncovered, at cool room temperature.) 8. Bake the casserole, uncovered, until the potatoes are hot, about 15 minutes. Arrange a rack 4 to 5 inches from the broiler and broil the casserole, watching constantly, until the potatoes start to brown, 1 to 3 minutes. Remove from the oven and garnish, if desired, with a few thyme sprigs before serving.