Season the shrimp with 1 pinch of kosher salt right before you start cooking.
Heat a wide cast iron pan or a 14-inch wok over medium-high heat, then add 1 tablespoon of canola oil.
Add sliced Taiwanese sausage and stir for 1 minute, then add shrimp and cook until both sides just turn pink (about 1 minute), then remove both from the pan and set aside.
Add sliced onions and carrots and cook for 2 minutes, stirring often, then add garlic, celery, napa cabbage, and snow peas, and cook for an additional 30 seconds.
Reduce the heat to low, add in 1 tablespoon of oyster sauce and 2 tablespoons of soy sauce, and stir for 1 minute.
Using a slotted spatula or spoon, remove all vegetables from the pan and set aside, leaving the sauce in the pan.
Add the chicken broth and bring to a simmer over medium-high heat.
Create a slurry by mixing 1 tablespoon of cornstarch in 1 cup of water, then add the slurry to the simmering chicken broth while stirring until thoroughly mixed.
Add the noodles to the pan and stir while gently pushing down on the noodles with a spatula. The noodles may look big in the pan but will cook down quickly. Flip the noodles with 2 spatulas if needed, and stir the noodles until they are almost cooked and most of the liquid is absorbed (about 3 minutes).
Add the sausage, shrimp, and vegetables back into the pan and stir to combine, then turn off the heat and serve.