Mix the mince with all the ingredients up to and including the pepper, knead well by hand until the ingredients have combined to form a compact mass. With wet hands, shape into 4 oval patties of approx. 1 cm thickness.
Heat a little oil in a frying pan and fry the patties for approx. 1 1/2 mins. on each side, remove.
Combine the gherkins with all the ingredients up to and including the pepper, set aside.
Arrange the lettuce on 4 slices of bread, place the patties on top, spread the tomato dressing over the patties, then top each with another slice of bread.