1) Cut and marinate the tofu cubes in soy sauce and lemon juice, one half hour, turn to season evenly.
2) Wash, cut or scice the morel mushrooms, broccoli, asparagus, celery, and onions into pieces.
3) In a wok or heavy skillet, heat the oil, stirfry onion and celery for about 3 min; add the mushrooms and broccoli, stirfry for about 2 min; lastly add the asparagus and stirfry for further 2 min on a gentle heat.
4) Place tofu on top of the vegetables alongwith the left over marinade; cover and leave for 2 min to warm the tofu.
5) Serve immediately over steamed brown rice.