Make chips: Toss potatoes in a large bowl with 2 tablespoons of oil, and pepper until well coated. Preheat oven to 450 degrees F. Arrange potato slices in 1 layer on 2 cookie sheets. Bake for 20 to 25 minutes until chips are crisped and lightly browned. Remove from oven, season with salt and cool.
Make dip: Heat oil over medium heat and add onions and scallion whites. Cook, stirring often, until golden brown and soft, about 10 minutes. Remove from heat and allow to cool.
If using regular yogurt, place it in a strainer lined with a paper towel and set the strainer over a bowl. Let the yogurt drain and thicken for 20 minutes.
Combine onions with thickened or Greek-style yogurt, mayonnaise, onion powder, garlic powder, salt, pepper and scallion greens and stir well to incorporate. Chill for 1 hour to let flavors meld. Serve with chips. Calories 250; Total Fat 13 g; (Sat Fat 2 g, Mono Fat 6 g, Poly Fat 5 g) ; Protein 9 g; Carb 26 g; Fiber 3 g; Cholesterol 5 mg; Sodium 320 mg Excellent source of: Vitamin C Good source of: Protein, Fiber, Vitamin B6, Vitamin K, Calcium, Manganese, Potassium