1 pound smoky kielbasa, quartered lengthwise and sliced 1/2 inch thick
4 tablespoons unsalted butter, melted
1 medium onion, halved and thinly sliced
2 garlic cloves, minced
1 pound red cabbage, finely shredded (6 cups)
1 large Granny Smith apple—peeled, cored and thinly sliced
2 tablespoons red wine vinegar
2 teaspoons chopped thyme
4 cups Turkey Stock
Kosher salt and freshly ground pepper
2 large eggs, beaten
Preheat the oven to 350°. Butter a shallow 9-by-13-inch baking dish. Spread the bread on 2 large baking sheets and bake until slightly dry, about 20 minutes.
Meanwhile, in a large, deep skillet, cook the kielbasa over moderately high heat, stirring occasionally, until browned, about 5 minutes. Transfer the kielbasa to a large bowl. Add 2 tablespoons of the melted butter to the skillet along with the onion and garlic and cook over moderate heat for 4 minutes. Add the red cabbage, apple, vinegar and thyme and cook, stirring occasionally, until the cabbage is wilted, about 6 minutes.
Add the cabbage mixture to the kielbasa. Stir in the toasted bread and Turkey Stock. Season with salt and pepper, then stir in the eggs. Spread the stuffing in the prepared baking dish and brush with the remaining 2 tablespoons of melted butter.
Cover the stuffing with foil and bake until set, about 45 minutes. Uncover and bake until the top is crisp, about 40 minutes longer. Let rest 15 minutes before serving.
The assembled stuffing can be refrigerated overnight. Bring to room temperature before baking.