Bali Burger with Caper-Green Peppercorn Mayo
1 tablespoon bottled-in-brine green peppercorns, drained
4 tablespoons capers, rinsed and drained
3/4 cup mayonnaise
6 tablespoons plain yogurt
5 tablespoons lime juice, divided
2 pounds ground beef chuck
6 medium cloves garlic, minced
3/4 cup chopped unsalted cashews
1/4 cup Tabasco sauce
3 tablespoons bottled minced ginger root
4 teaspoons ground cumin
2 teaspoons salt
Oil for brushing grill rack
6 (1/2-inch-thick) slices red onion
6 hearty seeded sandwich rolls, split
1 bunch watercress, tough stems discarded
Heat barbecue grill to medium-hot. Place peppercorns in a small food processor and process until finely chopped. Add capers and pulse until coarsely chopped. Transfer to a bowl and stir in the mayonnaise, yogurt and 1 tablespoon lime juice.
To make burgers, combine ground beef and the next 6 ingredients (through salt) and 4 tablespoons lime juice. Handling meat as little as possible, mix well and shape into 6 patties, formed to fit the rolls. Brush grill rack with oil and cook patties, covered, to desired degree of doneness, 5 to 7 minutes per side for medium. While burgers are cooking, push a long toothpick into side of each onion to keep slices together and brush both sides with oil. Grill until golden brown and crisp-tender, 2 to 3 minutes per side. During last few minutes of cooking time, place rolls cut sides down on edge of grill to lightly toast.
Spread mayo on cut sides of rolls. Place burgers on bottom halves and top with an onion slice and a generous amount of watercress. Replace roll tops.