Cook bacon in a large skillet or Dutch oven over medium heat until crisp and browned, about 12 minutes. Remove bacon from pan with slotted spoon and drain on paper towels. Discard all but 3 Tbsp rendered bacon fat.
Increase heat to medium-high and add onions and 1/4 tsp of salt. Cook onions until golden in color, making sure to stir occasionally and scrape sides and bottom of pan, about 20 minutes. Reduce heat to medium and continue to cook, stirring more often to prevent burning, until onions are deep golden brown, another 5 minutes. Add apples and continue to cook another 5 minutes. Transfer contents of pan to large bowl.
Add remaining 3/4 tsp salt, pepper, parsley, and sage to bowl and mix to combine. Add bread cubes.
Whisk stock and eggs together in small bowl. Pour mixture over bread cubes. Gently toss to evenly distribute ingredients.
Use as a stuffing or spoon into a greased baking dish. (If baking in a dish and moister stuffing is desired, add 1/4 to 1/2 cup more stock or broth to stuffing before spooning stuffing into dish.)
Bake at 350° F until the top has formed a crust and the stuffing is heated through, about 25 to 30 minutes. Serve hot.Servings: 12 cups