For this lamb burgers recipe, you'll want to splurge on good sturdy bakery buns that can absorb the extra liquid from the slaw and burger without disintegrating.

　　

Ingredients

Makes 4

　　

Lemon-Caper Aioli:

1/4 cup rinsed salt-packed capers

　　1 cup mayonnaise

　　2 tablespoons olive oil

　　1 teaspoon finely grated lemon zest

　　3 tablespoons (or more) fresh lemon juice

　　1 teaspoon Dijon mustard

　　2 garlic cloves, finely grated

　　Kosher salt

　　

Lamb burgers and assembly:

1 1/2 pounds ground lamb, preferably grass-fed

　　Kosher salt

　　4 tablespoons olive oil, divided

　　3 celery stalks, thinly sliced on the diagonal

　　1/2 fennel bulb, thinly sliced; plus 1/4 cup chopped fennel fronds (optional)

　　1/4 large sweet onion, thinly sliced

　　3 tablespoons fresh lemon juice

　　2 teaspoons crushed dried mint

　　Freshly ground black pepper

　　4 potato or ciabatta rolls, toasted

　　Boquerones (marinated white anchovies; for serving)

　　

Lemon-Caper Aioli:

Step 1

Place capers in a small bowl and pour in warm water to cover. Let soak 20 minutes. Drain, rinse, and pat dry. Coarsely chop.

　　

Step 2

Whisk capers, mayonnaise, oil, lemon zest, lemon juice, mustard, and garlic in a medium bowl; taste and season with salt and more lemon juice, if desired.

　　

Assembly:

Step 3

Shape lamb into 4 patties about 1" thick, season with salt, and let sit at room temperature 30 minutes.

　　

Step 4

Heat 2 Tbsp. oil in a large skillet, ideally cast iron, over medium. Cook lamb patties, working in batches if needed, until browned (they won’t take on as much color as a beef burger), 5–7 minutes. Turn and cook until browned on second side, about 5 minutes for medium-rare. Transfer patties to a plate and let rest 10 minutes.

　　

Step 5

Meanwhile, toss celery, fennel, fennel fronds (if using), onion, lemon juice, dried mint, and remaining 2 Tbsp. oil in a medium bowl. Season slaw with salt and pepper.

　　

Step 6

Generously spread aioli on cut sides of buns and build each burger with a lamb patty, 3 or 4 boquerones, and a mound of slaw. This is a messy burger, so the bib is not optional.

　　

Do Ahead

Step 7

Aioli can be made 1 day ahead. Cover and chill.