1 (2-inch) piece ginger, peeled and very thinly sliced
3 scallions, whites separated from greens, both cut into 2-inch pieces
3 tablespoons tender celery leaves, chopped
Small handful tender cilantro stems
Kosher salt and freshly ground black pepper to taste
Whisk together the stock, oyster sauce, soy sauce, and white pepper in a bowl. Season the shrimp generously with salt and pepper in another bowl. Place the noodles and shiitakes in a medium bowl, cover with warm water, and soak for 10 minutes; drain.
Heat 1 tablespoon vegetable oil in a claypot or another heavy-bottomed pot with a lid over medium heat, add the bacon, and cook until it is no longer pink and some of the fat is rendered, 5 minutes. Add the garlic, ginger, scallion whites and greens, and cilantro stems and cook, stirring, 5 minutes.
Add the noodles and mushrooms and toss to incorporate, then toss in the sauce, followed by the shrimp. Cover and cook until the shrimp begin to turn bright pink, 5 minutes.
Uncover, toss, close, and cook an additional 3 minutes. The bottom should get a little crispy; if not, cook a few minutes more. Uncover and garnish with the scallion greens and celery leaves.