New Zealand ground lamb patties are simply seasoned with salt and pepper and grilled to medium rare.They are served on rich brioche buns with caramelized onions, curry mayonnaise and peppery wild arugula.
Heat a large sauté pan over medium heat, add the olive oil and heat through. Add the butter and allow to melt. Add the onions and toss quickly to remove the moisture from the onions. Sauté, stirring occasionally, until the onions are soft and start to brown.
Sprinkle the salt and sugar over the onions (to help them caramelize) and reduce the heat to medium-low. Cook, stirring occasionally, until the onions are light brown and begin to caramelize, about 20 minutes.
Add the balsamic vinegar and stir to combine. Continue to cook until the onions are uniformly brown and caramelized, about an additional 10 minutes. Remove from the pan and set aside.
For the lamb burgers:
Divide the New Zealand ground lamb into 4 equal portions and flatten into patties, pressing an indent into the middle of each patty. Lay out on a parchment paper-lined baking sheet and season generously on both sides with the salt and pepper.
Prepare a grill to medium-high heat. Add the patties to the grill grates and cook, uncovered, for 3 minutes on each side for a medium rare burger.
Remove the burgers to a plate and let rest for 5 minutes.
For assembly:
In a small bowl stir together the curry powder, turmeric and mayonnaise until thoroughly combined.
Preheat the oven to broil on high. Arrange the brioche buns cut sides up on a baking sheet and broil until golden brown, about 1 to 2 minutes.
Add a lamb burger to each bottom bun. Top with some of the caramelized onion and a handful of arugula. Spread a tablespoon of the mayonnaise on the top half of the bun and close. Repeat with the remaining burgers. Serve immediately.