Step 1

Place 4 tablespoons of the unsalted butter and 1 cup whole milk on the counter. Place 1 tablespoon of the unsalted butter in a 9x13-inch or other 3-quart baking dish. Place 2 large eggs in a large bowl. Let everything sit at room temperature while you prepare the remaining ingredients.

Step 2

Arrange a rack in the middle of the oven and heat the oven to 300°F. Meanwhile, cut 10 ounces potato sandwich bread into 1/2-inch cubes (about 8 cups). Place on a rimmed baking sheet and spread out into an even layer.

Step 3

Bake until dried and light golden-brown, about 20 minutes. Meanwhile, prepare the potatoes.

Step 4

Peel 3 pounds russet potatoes. Cut into 1-inch cubes and place in a large pot. Add 1 tablespoon of the kosher salt and add enough cool water to cover the potatoes by about 1-inch. Bring to a boil over medium-high heat. Reduce the heat as needed to maintain a simmer and cook until the potatoes are fork-tender, 5 to 7 minutes.

Step 5

While the potatoes are cooking, dice 1 medium yellow onion (about 1 1/2 cups) and 2 large celery stalks (about 1 cup). Mince 3 garlic cloves. Pick the leaves from 5 fresh parsley sprigs and finely chop until you have 2 tablespoons. Finely chop 8 large or 12 medium sage leaves until you have 1 tablespoon. Pick the leaves from 2 fresh thyme sprigs and finely chop until you have 1 tablespoon.

Step 6

When the bread is ready, remove from the oven and set aside to cool. Increase the oven temperature to 375ºF.

Step 7

When potatoes are ready, drain and return to the pot. Add the 4 tablespoons softened butter. Let sit for about 1 minute to fully melt the butter. Mash 8 to 10 times with a potato masher or fork, leaving the potatoes chunky. Add the milk, 1 1/2 teaspoons of the kosher salt, and 1/2 teaspoon of the black pepper. Stir to combine.

Step 8

Melt 1 tablespoon of the unsalted butter in a large frying pan over medium-high heat. Add 1 tablespoon of the low-sodium chicken broth, the onions, and celery. Sauté until softened and translucent, 5 to 7 minutes. Add the garlic and sauté until fragrant, about 30 seconds. Add the parsley, sage, and thyme. Sauté until fragrant, about 30 seconds. Transfer the onion mixture to the pot of mashed potatoes.

Step 9

Add the remaining 2/3 cup chicken broth, 1/2 teaspoon poultry seasoning, remaining 1 1/2 teaspoons kosher salt, and remaining 1/2 teaspoon black pepper to the bowl of eggs and whisk to combine. Add the bread cubes and gently fold together until the bread cubes are just moistened (it’s OK if a few spots are still slightly dry). If the bread is too dry, stir in more broth a tablespoon at a time as needed.

Step 10

Transfer the bread to the pot of mashed potatoes. Gently fold to combine, being careful not to break up the bread cubes.

Step 11

Use your fingers or a brush to coat the baking dish with the now-softened butter. Transfer the bread mixture to the baking dish and spread into an even layer. Cut the remaining 1 tablespoon unsalted butter into thin slices and scatter over the top of the stuffing.

Step 12

Bake until the top is light golden and the bread cubes that are poking out are crisp to the touch, about 45 minutes. Let cool for 10 minutes before serving.