Start by draining the tofu and pressing it to remove excess moisture.
Toss the tofu cubes with a little cornstarch. Heat oil in a large skillet or wok over medium-high heat and cook the tofu for 5 minutes, or until golden and crisp on all sides. Transfer it to a plate and set aside.
In the same skillet, add a little more oil if needed. Stir fry the asparagus, bell peppers, and carrots for 5-7 minutes until they are tender-crisp.
In a small bowl, whisk together the soy sauce, sesame oil, honey or maple syrup, rice vinegar, garlic, ginger, and a little cornstarch mixed with water.
Return the tofu to the skillet with the vegetables. Pour the sauce over everything and toss gently until the tofu and vegetables are evenly coated and the sauce thickens slightly.
Top with green onions and sesame seeds if desired.