Wash and peel the russet potatoes. Cut them into thin strips to make fries. Soak the cut potatoes in cold water for at least 30 minutes to remove excess starch. Drain and pat the potatoes dry with a clean towel.

Heat the vegetable oil in a deep frying pan or pot over medium-high heat. Once hot (around 350°F), carefully add fries in batches. Fry until golden brown and crispy, about 5-7 minutes. Remove with a slotted spoon and place on paper towels to drain excess oil. Sprinkle with salt while still hot.

In a small bowl, combine sour cream, mayonnaise, Dijon mustard, crushed black peppercorns, lemon juice, and salt. Mix well until smooth and creamy. Adjust seasoning if needed.

In a large bowl, combine ground beef, garlic powder, onion powder, salt, and pepper. Mix gently until just combined. Form into 8 equal-sized patties, slightly larger than the burger buns.

Preheat a grill or frying pan over medium-high heat. Cook patties for about 3-4 minutes on one side. Flip and place a slice of cheddar cheese on each. Cook for another 3-4 minutes or until cheese is melted and patties are cooked to desired doneness.

Toast the burger buns lightly. On the bottom half of each bun, place a lettuce leaf, then two beef patties stacked, a tomato slice, and pickles. Spread creamy peppercorn sauce on the top half of the bun and place it on top to finish the burger.

Arrange the juicy double beef burgers on a platter alongside the crispy fries. Serve with extra creamy peppercorn sauce on the side for dipping.