1. To make the burgers, combine the beef mince, egg, salt, smoked paprika and pepper in a large bowl and mix well. Fry a small amount of the mixture in a hot frying pan and taste. Adjust the seasoning as needed.
2. Divide the mixture into 8 even-sized balls. Take one of the balls and flatten in your hand to form a flat patty, place 1/4 of the mozzarella in the middle of the patty and top with another mince ball. Flatten the ball with your other hand and crimp the edges of the two patties together to seal the cheese inside.
3. Place the patties on a greased tray and place in the fridge to chill for 30 minutes.
4. When the patties have been chilled, fry in a hot frying pan for 4-5 minutes per side (or until cooked to your liking).
5. Serve the patties on fresh rolls with rocket, caramelised onions and sliced tomato.