Place the soy sauce, garlic, ginger, monosodium glutamate (if using), salt, pepper, and sesame oil into a large resealable plastic bag and squeeze the bag with your fingers to mix the ingredients and dissolve the salt.
Add the chicken thighs to the marinade and squeeze the bag again to coat the chicken. Squeeze as much air as possible out of the bag and zip the bag closed. Refrigerate for 1 hour.
Mix the cornstarch and 2 tablespoons of water in a small bowl until smooth.
Pour the marinade from the plastic bag into a programmable electric rice cooker and mix in the cornstarch mixture until thoroughly combined.
Place the chicken thighs into the sauce.
Add just enough water to barely cover the chicken and stir.
Close the lid of the cooker, set the cooker for the regular rice setting, and press the start button. When steam begins coming out of the top of the cooker (after about 20 minutes), set the cooker's timer for 10 minutes. When the timer goes off, uncover and stir the chicken. Set timer and cook for another 10 minutes; switch the cooker to the keep-warm setting. Allow chicken to rest in the keep-warm setting for 20 minutes before serving.
