1. Soak bamboo skewers in water at least 30 minutes.
2. Combine sesame seeds and next 3 ingredients in a shallow plate. Cut tuna against the grain to make 3-inch-wide x 1 1/2-inch-thick strips. Rub 1 tablespoon vegetable oil on all sides of tuna, and roll in sesame seed mixture.
3. Heat remaining 2 tablespoons oil in a heavy skillet over medium-high heat. Sear tuna 1 to 2 minutes on each side. Remove from heat, and refrigerate immediately to stop fish from cooking. (Tuna should be rare in center.)
4. Slice tuna across the grain into 1/2-inch slices. Thread 2 pieces on each bamboo skewer, and transfer to a platter. Drizzle with 2 tablespoons Wasabi Aïoli, and serve with remaining aïoli.