Combine potatoes with salted water in a large saucepan.

Simmer until tender, about 20 minutes.

Cook bacon in a skillet until browned and crisp.

Transfer bacon to paper towels to drain.

Drain potatoes and let cool slightly.

Cut potatoes into eighths.

Combine potatoes and bacon in a bowl; keep warm.

Pour off excess fat from skillet, leaving 3 tablespoons.

Sauté onion in the skillet until softened, about 3 minutes.

Add sugar, 2 tablespoons vinegar, and beef broth.

Simmer for 2 minutes.

Add onion mixture to potatoes with parsley and remaining 1 tablespoon vinegar.

Toss gently and season with salt and pepper.

Serve warm or at room temperature, garnished with parsley.