Fire up the grill - nice and hot, mine was 220ºc - I've a gage on mine.
Make the burger sauce, add all the ingredients to a bowl and mix.
Break the burgers in half and press into the tortillas, make them even and push to the edges. Wash your hands. Season with salt and garlic granules if you have some.
Put the tortilla on the grill meat side down, use a burger press or small pot as a weight. Cook for 4-5 minutes then flip, add a slice of cheese and toast for 1-2 minutes on the other side. Don't walk away from the grill - or it will burn!!
Top with the gherkins, chopped onions, lettuce and burger sauce!