This is a hearty side dish, or when doubled, a fine salad supper.
Prepare medium-hot charcoal fire, or preheat gas grill (or broiler).
Wrap tofu in paper towels, and squeeze gently to remove excess water. Pat dry. Slice into 3 pieces horizontally; cut each piece in half. Set aside.
Mix together soy sauce, sesame oil, mirin, vinegar, chili paste and garlic in 9×13-inch glass baking dish. Add tofu, turn over to coat and let sit 15 minutes.
Spray tofu with cooking spray on all sides, and grill until browned and crusty, 3 to 4 minutes per side. Arrange arugula on large serving platter, then arrange grilled tofu on top of arugula.
Meanwhile, add green beans and onion to remaining vinaigrette, and toss to coat. Grill beans and onion on perforated rack, stirring frequently, until beans are tender and browned, 8 to 10 minutes. Arrange beans and onion on top of tofu. Pour any remaining vinaigrette on salad. Serve.