German potato salad

Ingredients:

1 pound (3 medium) potatoes
6 slices bacon, diced
1 medium-size onion, diced
1/2 cup vinegar
1/2 cup stock or bouillon
1 tsp. salt
1/4 tsp. pepper
1 tsp. sugar
1 egg yolk, beaten

Preparation:

Scrub potatoes. Rinse.
Boil in jackets. Let cool.
Peel and cut in 1/4-inch slices.
Cook bacon in hot pan until crisp.
Add onion. Stir and cook until transparent.
Add vinegar, stock or bouillon and seasonings.
Stir. Let come to a boil.
Stir in egg. Remove from heat and pour over potatoes.