Dice tofu into small cubes and gently toss with cornstarch.
Mix together sauce and set aside.
In a medium skillet, heat a drizzle of oil over medium high heat. Add mushrooms to the skillet and cook 1-2 minutes. Toss in green beans and cook until mushrooms are browned and beans are tender. Removed from pan and set aside.
Coat tofu cubes in egg then panko and pan fry in remaining oil over medium heat. This should take 4-5 minutes and tofu should be browned all over.
Turn heat to medium-low and return veggies to pan. Drizzle stir-fry sauce in and stir gently to coat. Use water to thin sauce if necessary.
Serve immediately over rice or noodles and garnish with fresh basil and sesame seeds, if desired.