1. Preheat the oven to 350°.
2. Lightly coat 6 (8-ounce) ramekins lightly with cooking spray. Spread bread cubes in an even layer on a baking sheet, and lightly coat with cooking spray. Bake at 350° for 10 minutes or until bread is crisp and lightly browned, stirring after 5 minutes.
3. Heat a small skillet over medium heat. Coat pan with cooking spray. Add onion, 1/4 teaspoon salt, and 1/8 teaspoon pepper to pan; cook 10 minutes or until onion is tender. Increase heat to medium-high. Stir in 2 tablespoons water, and cook 5 minutes or until golden brown, stirring frequently. Evenly divide onion among prepared ramekins; top with croutons. Sprinkle remaining 1/4 teaspoon salt and remaining 1/8 teaspoon pepper evenly over croutons.
4. Carefully break 1 egg into each ramekin on top of croutons; drizzle 2 teaspoons half-and-half over each egg. Arrange ramekins in a roasting pan lined with a dish towel (to anchor them in the pan). Pour boiling water halfway up the sides of the ramekins to make a water bath. Bake at 350° for 15 minutes or until the whites are almost set. They should be slightly underdone as they will continue cooking in the hot dishes when you take them from the oven. Garnish with flat-leaf parsley sprigs, if desired.