Ingredients
1 cup white miso (also called shiro miso)
1/2 cup mirin (Japanese sweet rice wine)
1/2 cup sugar
1/4 cup water
1/2 cup mayonnaise (try plain yogurt)
2 lb tuna steak, cut into 1-inch cubes (Pre-frozen is OK)

Preparation
Heat miso, mirin, sugar, and water in a small saucepan over medium heat, stirring, until sugar has dissolved. Remove from heat and whisk in mayonnaise, then cool to room temperature. (Don't have to heat)

Put tuna in a sealable bag. Pour marinade over tuna and marinate, chilled, at least 1 hour.

Prepare grill for direct-heat cooking over hot charcoal (high heat for gas).

Thread tuna onto skewers, leaving a small space between each piece. Put on a tray.

Generously oil grill rack, then grill skewers, turning once, until just pink in center, about 4 minutes total. Let stand 5 minutes.

Notes
• Tuna can be marinated up to 24 hours.
• Tuna can be broiled on an oiled broiler pan 4 to 6 inches from heat, turning once.