Whisk the stock, water, nuoc cham, maple syrup, corn starch and sriracha together in a small bowl and set aside for later.
Butterfly the chicken breasts in half and then cut into strips the size of tenders. Then, cut those tenders in half.
Set a wok or pan on high heat, pour the oil into the pan and sear the chicken breasts in 2 batches for 3 minutes or until it starts to brown. Salt & pepper them and continue cooking.
After 2 minutes, pour the sauce around the rim of the wok and turn off the heat when the sauce thickens and bubbles. Add the celery and bell peppers into the mix when you do and let the residual heat cook the vegetables.
Taste for seasoning and serve on top of rice with coriander garnishing.