Preheat the oven to 200 degrees F. Drain the tofu well and cut into 8 slices. Set the slices on paper towel and gently pat dry. Heat your barbecue or indoor grill to medium-high. Brush the tofu with 1 1/2 Tbsp. of the oil.
Brush the bars of the grill lightly with oil. Grill the tofu 1 to 2 minutes per side, arrange on a heatproof platter, and keep warm in the oven.
Heat the remaining 1 1/2 Tbsp. of oil in a wok or large skillet. Combine the teriyaki sauce, vegetable stock or water, and cornstarch in a small bowl and set aside.
When the wok or skillet is hot, add the onion, celery and broccoli and stir-fry 2 to 3 minutes. Add the garlic, ginger and bok choy and stir-fry 1 to 2 minutes more. Pour the teriyaki mixture into the wok or skillet, bring to a simmer and cook until a lightly thickened sauce forms around the vegetables, about 1 minute. Spoon the vegetables over the tofu and serve.