Begin by making a marinade for the chicken. In a small bowl, combine the soy sauce, corn starch, rice vinegar, ginger, and five spice powder.
Place the drumsticks and mushrooms in a large bowl and add the marinade to the bowl as well. Toss the chicken and the mushrooms to completely coat them in the marinade. Let the mix sit for about 15 minutes to really soak the flavors of the marinade into the chicken.
Add the rice, salt and the water to the bowl of the instant pot.
Add the marinated chicken and mushrooms to the instant pot as well along with the bok choy. No need to mix everything together, the instant pot will do that for you!
Seal the lid on the instant pot and press the 'manual' button. Set the instant pot to cook for ten minutes on high pressure. The pot will take about 15 minutes to heat up before the timer begins (about 20 minutes if you are making the larger batch recipe).
Once cooked, let the instant pot naturally release the pressure for 15 minutes then, manually release the remaining pressure by carefully opening the pressure latch.
Serve while the food is nice and hot!