Clean and scrub baking potatoes. Bring a large pot of salted water to a boil. Add potatoes and cook until tender but still firm, about 15 minutes. Drain, cool and cut into thick slices; place slices in a large bowl.
Place bacon in a large, deep skillet. Cook over medium high heat until crisp. Stir the onion and celery into the skillet and cook gently until the vegetables turn yellow.
Dissolve the bouillon cube in boiling water and stir in the vinegar, salt and pepper. Pour the broth mixture into the skillet with the bacon/onion mixture and bring the water to a boil.
Add the egg slowly, stirring until the mixture is slightly thickened. Pour the vegetable mixture over the potatoes, add parsley and toss lightly.