Put mince in a bowl for the burger patties. Season with 2-3 tsp salt and 1-2 tsp pepper. Form 8 flat burger patties (as big as the buns) from the mince with moistened hands.
Heat 2 tablespoons of oil in a coated frying pan. Fry 4 patties in it all around for 8-10 minutes. Remove. Heat 2 tbsp. oil again and fry the remaining patties in the same way.
Clean the lettuce, cut into individual leaves, wash and shake dry. Wash the tomatoes, cut them into thin slices. Peel onion, cut into fine rings.
Preheat oven grill to 200 °C. Grate and mix both cheeses. Spread patties on a baking tray lined with baking paper. Sprinkle with the cheese mixture and bake under the grill for approx. 2 minutes.
Cut the burger buns in half horizontally. First spread the lower halves of the buns with 1 tbsp. ketchup or barbecue sauce, then cover with lettuce, tomato slices, onion rings, jalapeños and burger patties.
Top with 1 tablespoon each of ketchup and barbecue sauce. Place the upper roll halves on top and bite into them immediately.