Simmer 1 1/2 pounds diced red potatoes in salted water until tender; drain. Cook 4 slices chopped bacon until crisp; drain, reserving 2 tablespoons drippings. Add 1 bunch chopped scallions; saute. Whisk in 1/4 cup water, 2 tablespoons white wine vinegar and 2 teaspoons each dijon mustard and sugar; bring to a simmer. Toss in 1/4 cup each chopped parsley and cornichons, the potatoes and bacon; season with salt and pepper.