- Stir together mayonnaise, onion, pickles and lemon juice in a medium bowl. Season to taste with salt and pepper then chill for at least 10 minutes.
- Heat the vegetable oil in a deep pan and cook the burger patties to brown golden color on both sides. Place them in a plate aside.
- Meanwhile, fry the fries in a deep-frying pan with vegetable oil until crispy and set aside on kitchen papers.
- Spread butter equally on each inner side of the sliced bun and place it down on a hot pan to have golden color.
- Place one jumbo smoky grill beef patty on a bottom slice of a bun, top it with sauce au poivre and crispy fried onions.
- Place the top bun to form a burger and serve it warm with crispy fries of your choice and enjoy!