Combine the beef mince, parmesan, mozzarella and cheddar. Season with salt and pepper. Mix lightly, shape into four burgers. Brush or spray the burgers lightly with oil.
Preheat a non-stick pan to moderately high. The burgers should sizzle when you add them to the pan, lower the heat to moderate. Cook for 6-7 minutes on each side or until thoroughly cooked. Turn them once only.
Top the base of the rolls with rocket, tomato, cooked beef burger, sauce and onion. Replace roll top. Serve beef burgers with sweet potato fries.
Burgers should not be served undercooked, rare or pink. A good guide is that when a skewer is inserted into the thickest part of the burger the juices run clear.
Beef burgers can be barbecued also. Cook over a moderate heat for 5-6 minutes each side.
Try using any combination of your favourite cheese for the beef burgers such as blue cheese, feta, gouda or Swiss.
You can used purchased frozen sweet potato fries if desired or make your own by cutting 600g sweet potato into chips, coating in a little oil and baking at 220⁰C for 30-35 minutes.
You can serve the beef burgers with potato wedges if preferred.