Preheat oven to 300 degrees.
Arrange bread cubes sheet pan and bake for 7 minutes, until they start to turn golden brown. You want them to be a little bit crispy.
While the bread is toasting in the oven, melt butter in a 12 inch skillet. If you’re doubling the recipe, you may need a larger skillet. If you don’t have a larger skillet, use two skillets. Add celery, onions, apples, parsley, rosemary, 2 teaspoons salt, and 1/2 teaspoon pepper. Cook 10 to 15 minutes or until softened, stirring occasionally.
In large bowl, toss bread with vegetable mixture and broth. Transfer to 3-quart baking dish. If you’re doubling the recipe, use two 3 quart baking dishes.
Cover with aluminum foil and bake 30 minutes. Uncover and bake another 15 to 20 minutes or until top is golden.