1. Remove grill rack, and set aside. Prepare grill for indirect grilling, heating one side to medium-high and leaving one side with no heat. Place grill rack on grill.
2. Combine 3 cups water, Dijon mustard, and the next 5 ingredients (through bay leaves) in a large saucepan. Bring to a boil, and cook for 2 minutes. Add potatoes and onions; bring to a boil. Reduce heat to low, and simmer for 12 minutes. Remove from heat, and let stand for 10 minutes in cooking liquid; drain. Cut onions in half.
3. Pierce the bottom of a disposable aluminum foil pan several times with the tip of a knife. Place the potatoes and onions in pan, and coat with cooking spray. Place pan on grill rack over unheated side of grill; cover grill, and cook for 25 minutes or until lightly browned.
4. Heat a large nonstick skillet over medium-high heat. Coat pan with cooking spray. Add sausage, and sauté for 4 minutes or until lightly browned. Combine sausage, potato mixture, parsley, and salt in a large bowl; toss gently.