lamb burgers with watercress and creamy mint sauce

I mixed ground lamb and beef  - about equal portions - and formed into slider sized patties.  Seasoned them with salt, pepper, and garlic powder.  I grilled them on a hot grill about 4 minutes per side and toasted the buns.  The mint sauce was 1/3 c. mayonnaise, 1/2 c. plain Greek yogurt, 1/4 c. packed fresh mint, a chopped shallot, and 1 tsp. of Worcestershire all blended until creamy. I served the burgers on the toasted buns with cucumber slices, the mint sauce, tomato slices, and watercress.