Prepare the noodles according to package instructions. You can prepare the rest of the recipe as the noodles are cooking and drain them and set them aside until you're ready to use.
Heat the avocado oil over medium-high heat in a large skillet or pot. Add the chopped chicken and brown 4 to 5 minutes. The chicken does not need to be cooked all the way through just yet, just browned. Transfer the chicken to a bowl and set aside.
Add the cabbage to the skillet, cover, and cook for 3 to 4 minutes, until wilted, stirring occasionally. Note: if needed, add more oil to the skillet.
Add the carrots, celery, and garlic and sauté, stirring frequently, until vegetables are fragrant and softened, about 2 to 3 minutes.
In a bowl or measuring cup, whisk together the ingredients for the sauce.
Transfer the chicken back to the skillet with the vegetables, along with the noodles and sauce.
Toss everything together until noodles are well-coated in sauce and much of the liquid has burned off, about 4 to 5 minutes. I use tongs for this process, as it makes it easier to get the noodles to combine with the sauce and other ingredients.
Notes
*replace the oyster sauce with 1 tsp fish sauce or 1 tablespoon hoisin sauce.