In a large skillet over medium heat, heat the olive oil. Add the onions and saute until soft and translucent. Then add the garlic and stir for another minute or two.
Add the beef and cook, breaking up with a wooden spoon or spatula as you go. Once the beef is cooked, add the tomato sauce and stir until heated. Season with salt and pepper.
Lay some fries on a plate, then spoon the beef mixture over the fries.
Sprinkle shredded cheddar and shredded mozzarella over the fries, then squeeze the mayonnaise and ketchup over the plate to your preference.