In a large saucepan, bring greens and 2 cups water to a boil. Reduce heat; cover and simmer for 4-8 minutes or until tender. Drain and set aside.
In a large skillet, cook bacon over medium heat until crisp. Using a slotted spoon, remove to paper towels; drain, discarding drippings.
In a small bowl, combine flour and sugar; stir in the milk, salt and remaining water until smooth. Pour into skillet and bring to a boil; cook and stir for 2 minutes or until thickened.
Stir a small amount of hot mixture into egg yolks; return all to the pan, stirring constantly. Bring to a gentle boil; cook and stir 2 minutes longer. Add the vinegar, greens and bacon; heat through. Serve over mashed potatoes. Yield: 4 servings.