- 1 pound applewood-smoked bacon slices, coarsely chopped (about 4 cups)
- 2 3/4 cups (or more) low-salt chicken broth, divided
- 1/4 cup (1/2 stick) butter
- 4 cups finely chopped onions
- 6 cups 1/2-inch pieces peeled cored sweet-tart heir loom apples (such as Arkansas Black; about 5 large) or other sweet-tart apples (such as Pink Lady)
- 2 cups finely chopped fresh fennel bulbs
- 1 cup finely chopped celery
- 1 teaspoon coarse kosher salt
- 3/4 teaspoon freshly ground black pepper
- 3 large eggs, beaten to blend
- 2/3 cup chopped fresh Italian parsley, divided
- Preheat oven to 350°F. Spread bread cubes on 2 large rimmed baking sheets. Toast until light golden and crisp around edges, about 20 minutes. Cool completely.
- Preheat oven to 425°F. Combine bacon and 4 cups water in large saucepan; bring to boil. Reduce heat; simmer 10 minutes.
- Drain, discarding liquid. Place bacon in large roasting pan. Pour 2 cups chicken broth over. Roast until broth evaporates and bacon begins to crisp around edges, stirring occasionally, about 45 minutes.
- Meanwhile, melt butter in large nonstick skillet over medium-high heat. Add onions and 1 cup water; bring to boil. Reduce heat to medium; simmer until water evaporates, stirring occasionally, about 15 minutes. Reduce heat to medium-low; sauté until onions are soft, about 5 minutes longer.
- Remove roasting pan with bacon from oven; reduce oven temperature to 375°F. Mix cooked onions, apples, fennel, and celery into bacon in roasting pan. Roast until apples and all vegetables are tender, stirring occasionally, about 1 hour. Cool slightly. DO AHEAD: Can be made 1 day ahead. Store toasted bread in large resealable plastic bags. Chill bacon-apple mixture uncovered until cool, then cover and keep chilled. Let stand at room temperature 1 hour before continuing.
- Preheat oven to 375°F. Butter 13x9x2- inch glass baking dish. Combine toasted bread, 3/4 cup chicken broth, and baconapple mixture in very large bowl. Mix in 1 teaspoon coarse salt and 3/4 teaspoon pepper. Mix in eggs, then 1/2 cup parsley. Add more chicken broth by 1/4 cupfuls if mixture is dry. Transfer to prepared dish. Cover dish with buttered foil; bake 35 minutes. Uncover; bake until top is browned, about 30 minutes longer. Sprinkle with remaining parsley.