Mix the minced meat with a finely chopped onion, the tsp. breadcrumbs and the beaten egg. Knead well to obtain a uniform consistency.
First form 6 meatballs of the same size, which you then flatten into a burger meatball.
Place the burger meatballs in a pan over medium heat and fry them evenly until they are crispy brown.
Meanwhile, cut the remaining ingredients into burger-sized pieces. Slice the tomatoes and cucumber and the onion into rings.
Place the burger buns in the preheated oven at about 140° for about 4 minutes.
Last but not least, you assemble your burger. My tip is to mix the ketchup and mustard on the top and bottom of the burger, then add the onions, cucumber and lettuce. Then put the burger meatball in the middle, cheese on top of the meatball and round it all off with a little garlic sauce.