Spray a medium frying pan with low calorie cooking spray and place over a medium heat.
Add the beef mince, paprika, garlic and onion granules and fry for 8 minutes until the juices have evaporated and the beef is cooked through. Season to taste with salt and pepper.
Spread the tortilla chips over a baking tray and add the beef on top.
Add the gherkins and tomato and sprinkle over the grated cheese. Pop under the grill for 2-4 minutes until the cheese has melted.
While the nachos are under the grill, add the mayonnaise, tomato ketchup, mustard and gherkin pickle vinegar to a small bowl and mix until smooth.
Spoon the burger sauce over the nachos and top with the shredded lettuce. Serve!