Butter a 9×13-inch baking dish. Place the dried bread chunks, additional cranberries, and chopped walnuts in a very large mixing bowl.
Butter
In a separate bowl, whisk the eggs. Add the milk, cream, granulated sugar, brown sugar, vanilla, cinnamon, nutmeg, and salt. Whisk until thoroughly combined.
8 large eggs, 3½ cups whole milk, 1½ cups heavy whipping cream, 1 cup granulated sugar, ½ cup packed dark brown sugar, 2 teaspoons vanilla extract, 1 teaspoon ground cinnamon, ½ teaspoon freshly grated nutmeg, ½ teaspoon kosher salt
Pour the custard over the bread and gently stir to coat. Let the bread soak for 10 minutes. Transfer to the prepared baking dish, spreading the cranberries and walnuts evenly throughout. Press the bread down lightly.
1 lb cranberry walnut bread loaf, ½ cup dried cranberries, ½ cup chopped walnuts
Cover and refrigerate for at least 4 hours, preferably overnight.
Preheat the oven to 350°F. Uncover and bake for 1–1½ hours, until puffed, golden brown, and set in the center, with an internal temperature of 160–165°F. Begin checking at 1 hour and loosely tent with foil if needed to prevent excessive browning.
Let rest for 15–20 minutes before serving.
For the sauce, melt the butter in a saucepan over medium heat. Whisk in the brown sugar, cream, bourbon, orange zest, orange juice, and salt. Simmer, whisking often, until thickened, about 3–5 minutes.
½ cup unsalted butter, ¾ cup packed dark brown sugar, ¼ cup heavy whipping cream, ¼ cup good-quality bourbon, 1 tablespoon finely grated orange zest, 1 tablespoon fresh orange juice, 1 pinch kosher salt
Cool the sauce slightly and spoon over individual servings.