Put potatoes in a large saucepan, cover with water and bring to a boil. Cover, reduce heat, and continue cooking until potatoes are tender but still firm, about 15 to 20 minutes.
In a large skillet, heat the 2 tablespoons of bacon drippings and vegetable oil over medium heat. Add the sliced onion and saute until tender and lightly browned, about 4 to 6 minutes. Stir in the flour, sugar, salt, and pepper. Cook, stirring, for 1 minute. Add the water and continue cooking for 3 minutes. Add the vinegar and parsley and cook for 1 minute longer. Taste and add salt and pepper as needed.
Pour the onion dressing mixture over the potatoes and add the bacon. Gently stir to combine.
Calories per serving: 292