Heat grill to medium heat.
Grill chicken and peppers 10 min. or until peppers are evenly blackened, turning occasionally. Place peppers in closed paper bag or covered bowl. Grill chicken an additional 15 min. or until done (165°F). Meanwhile, cook spaghetti as directed on package.
Remove and discard peels, stems, seeds and veins from peppers. Drain spaghetti, reserving 1 cup of the water; pour water into blender. Add peppers, sour cream and bouillon cube; blend until smooth. Pour into Dutch oven or large deep skillet.
Add spaghetti and Singles pieces; cook and stir on medium heat 3 min. or until Singles are melted and mixture is heated through. Serve topped with chicken and parsley.