This recipe, inspired by a traditional Pennsylvania Dutch dish, takes the best parts of mashed potatoes and stuffing and combines them into one. It's as homey and comforting as a Thanksgiving side can get. Use a good quality white country bread with some texture to it for best results.
Preheat the oven to 375˚ F and butter a 9-by-13-inch or other 3-quart baking dish. Put the potatoes in a large pot; cover with water and season with salt. Bring to a simmer; cook until the potatoes are tender, 12 to 15 minutes. Drain and keep warm.
Meanwhile, spread the bread on a baking sheet and bake until lightly toasted around the edges, about 5 minutes.
Combine 1 tablespoon butter and the sausage in a large skillet over medium heat. Cook, breaking up the meat into pieces with a wooden spoon, until browned, about 4 minutes. Add 7 tablespoons butter, the onion and celery; season with 1/2 teaspoon salt and a few grinds of pepper. Cook, stirring occasionally, until the vegetables are softened, about 8 minutes. Stir in the thyme, sage and poultry seasoning, then add the chicken broth and bring to a simmer. Remove from the heat and set aside.
Whisk the half-and-half with the eggs, 1/2 teaspoon salt and a few grinds of pepper in a large bowl. Add the warm potatoes and mash; season with salt. Mix in the bread and the sausage mixture. Melt the remaining 2 tablespoons butter in the microwave. Transfer the stuffing mixture to the baking dish, then drizzle with the melted butter. Cover with foil and bake 30 minutes, then uncover and continue baking until the top is crisp and golden, 20 to 25 more minutes.