1In 12-inch heavy skillet, melt butter over medium-high heat until sizzling. Cook onions in butter 5 to 6 minutes, stirring frequently, until onions are softened. Stir in sugar and vinegar. Cook 9 to 10 minutes, stirring frequently, until onions are very soft and light golden brown. Cool onion mixture slightly, about 10 minutes.
2Set oven control to broil. Place bread slices on cookie sheet. Broil with tops 4 inches from heat 1 to 2 minutes or until lightly browned. Turn bread; broil 1 to 2 minutes longer or until lightly browned.
3Spread about 2 teaspoons cream cheese on each bread slice. Top each with 1 tablespoon onion mixture; sprinkle with small amount parsley.