Cut the onion and pickled cucumber into small cubes and place in a small bowl. Pour the mayonnaise, ketchup and mild mustard over them and mix until smooth. Season with salt and pepper to taste.

Cut the iceberg lettuce into thin strips.

Divide the minced meat into three equal pieces and place on top of the tortillas. Press the minced meat evenly over the tortilla so that the entire tortilla is covered with minced meat to the edges. Repeat the process with all three tortillas (if you use larger tortillas, there will be enough minced meat for two taco burgers). Season the minced meat evenly with salt and pepper.

Heat a pan over high heat and coat with a thin layer of olive oil. Place the minced meat-covered tortilla, meat side down, in the pan and fry for ~2 minutes, until the minced meat has turned brown. Turn the heat down, flip the taco burger over in the pan, place a slice of melted cheese on top and cover the pan with a lid. Let the taco burger fry for about a minute, until the bottom of the tortilla has turned brown and the cheese has slightly melted. Remove the taco burger from the pan and repeat the same process with the remaining tacos.

Place the sauce and iceberg lettuce on top of the taco burgers and fold them together. Garnish with sesame seeds if desired and cut in half down the middle for easier eating. Enjoy!