Ingredients
For burgers:
1 1/2 pounds yellowfin tuna, cut into 1-inch pieces, chilled
1 1/2 teaspoons minced garlic
1 1/2 teaspoons minced ginger
1 1/2 teaspoons finely grated lemon zest
3 tablespoons Dijon mustard
1 teaspoon coarse salt
1/2 teaspoon freshly ground pepper
1 tablespoon vegetable oil
For coleslaw:
2 tablespoons rice-wine vinegar
1/2 teaspoon sugar
1/2 teaspoon coarse salt
1/2 cup grated carrot (from 1 carrot)
1/2 cup grated radish (from 3 to 4 radishes)
1 cup cored and thinly sliced Napa cabbage (from 1/2 head cabbage)
1 scallion, thinly sliced diagonally
1/2 teaspoon black sesame seeds
For assembly:
1/3 cup mayonnaise
4 braided challah rolls, split
Preparation
For burgers: Fit a food grinder with a grinding plate with about 1/4-inch holes. Grind tuna into a bowl. Add garlic, ginger, lemon zest, mustard, salt, and pepper. Mix gently, and shape into four 1-inch-thick patties. Cover, and refrigerate until cold and firm, about 30 minutes.
For coleslaw: Whisk vinegar, sugar, and salt in a small bowl. Mix carrot, radish, cabbage, scallion, and sesame seeds in a medium bowl. Toss slaw with vinegar mixture, and refrigerate up to 1 hour.
Heat oil in a large nonstick skillet over medium heat. Cook patties to medium-rare, about 2 minutes per side. Wipe skillet clean, and return to heat. Spread mayonnaise on cut sides of roll halves, and heat, mayonnaise side down, until golden, about 1 minute. Divide burgers and slaw among bottom halves of buns. Sandwich with top halves.
