Stovetop Sweet and Sour Coleslaw Dressing Recipe

My mother made her coleslaw dressing with several ingredients she cooked on the stovetop. I know she used an egg, some vinegar and sugar; probably salt and pepper, too. (I do remember her saying it was important not to cook the egg but blend it into the other ingredients.) But I don’t know how much of each or what other ingredients were used. I did not bother learning how to cook when I was growing up and sorely regret it.