1. Combine chicken stock and eggs. Add toasted sourdough bread cubes.
2. Heat a nonstick skillet over medium-high heat. Add olive oil; swirl. Sauté onion for 2 minutes. Reduce heat to low; cook 30 minutes. Cool slightly. Add onion, ham, Gruyère cheese, and parsley to bread mixture.
3. Bake stuffing at 350° for 45 minutes in an 11 x 7-inch baking dish coated with cooking spray.