Warm the oil in a large pan, then saute the beef until cooked through.
While the beef is cooking, chop onion, tomatoes and pickles for the salad. For the pickles, separate about 2 tbs and cut them until they are almost minced for the sauce. Grate the cheese - it's better freshly grated than pre-shredded!
Remove beef and add onions to the pan. Saute onion 5-10 minutes until slightly browned but not burnt.
While the onions are sauteing, add all sauce ingredients plus 2 tbs minced pickles to a bowl and whisk until smooth (minus the pickles).
Serve by layering the lettuce first, then topping with beef, onion, cheese, pickles and tomatoes. Drizzle sauce on top and optionally garnish lightly with sesame seeds.