Preheat your oven to 350 degrees F. Fill a large, heat-safe mixing bowl with the bread, and set aside. Grease the 9x13x2″-inch baking dish and set aside.
In a large, cast iron skillet, over medium-high heat, melt 3/4 cup of unsalted butter. When it’s melted, add the onions and celery, stirring to coat the vegetables with the butter.
In a 2-cup wet measure, add 1 1/4 cups broth, add 2 eggs and whisk until combined. Add to the cooled bread mixture and fold in until it’s fully incorporated.