Chop the vegetables very finely - if the pieces are too big, the mixture will not stick together. Combine the rice and vegetables in a bowl. Mix the tahini, lemon juice, tamari and tofu in a blender until smooth and creamy. Pour this sauce over the rice and vegetables and mix thoroughly. Preheat the oven to 180 degrees Celsius.
With wet hands, roll bits of the rice mixture into balls of about 5cm in diameter. Roll the balls in the sesame seeds until they are completely coated and place them on a baking tray. Bake for 40 minutes, turning the balls twice during the baking process.
While the balls are cooking, make the dipping sauce by mixing the tamari and mirin together in a small bowl. Serve the rice balls with Asian salad and a separate dish of dipping sauce on the side.