Cut the chicken breasts in half crosswise and then slice them into thin strips. Set aside.
Stir together the ingredients for the marinade ingredients, then add the reserved chicken to it.
Let the chicken marinate while you prep the vegetables and cook the noodles.
In a large saucepan, bring about 4 cups of salted water to the boil and then add the rice noodles to it. Cook for 3 minutes and then drain the rice noodles and plunge them in a bath of cold water to stop the cooking. When the noodles are cold, strain them and set them aside.
In a wok or large heavy skillet, heat half the coconut oil over medium-high heat until really hot, about 1 minute. Add vegetables and cook, sautéeing almost constantly, until the veggies start to soften slightly and become fragrant, about 1 minute. Transfer to a bowl and return the wok to the heat source.
Add the rest of the coconut oil as well as the chicken and marinade to the wok and cook until the chicken becomes completely opaque, about 4 minutes.
Add the vegetables and noodles to the wok and mix delicately until the ingredients are well distributed and the noodles are heated all the way through, about 1 minute.
Serve, garnished with a pinch of toasted sesame seeds, some chopped green onion and a squirt of sriracha sauce, if desired.
*To make chicken breasts easier to slice, place them in the freezer for 30 to 45 minutes before cutting them.