Combine the marinade adding the cornstarch last and making sure to whisk it in so there are no lumps. Add the chicken and tofu. Gently mix all the ingredients to they are coated. Let them marinate for 20 minutes and up to 1 hour.
Combine the sauce ingredients in a measuring cup and, again, whisk in the cornstarch.
Drain the chicken and tofu, do not rinse it.
Heat a large 16 inch wok or a 14 inch skillet over high heat. Bring all your ingredients to the stove on a sheet tray so you are really prepared because this goes quick and you need everything by your side.
Add the oil and let it begin to smoke. Add the drained chicken and tofu. Let it caramelize.
Add the celery and cashews. Let the cashews get brown on the tips then add the garlic.
Once the garlic is fragrant add the spinach and the sauce. Let the sauce come to a boil and wilt the spinach all the while gently stirring.
Make sure the chicken is done and everthing is hot. Taste and adjust the seasoning if you need to by adding a drop or two of soy or a pinch of salt. Serve over rice.