Soak the glass noodles in room temperature water for 10 minutes while you prep everything else. Drain well. They should be pliable but still a bit firm; they finish cooking in the pot.
Mix the sauce. In a bowl, stir together the oyster sauce, light soy, dark soy, sugar, sesame oil and stock until the sugar dissolves. Toss the drained noodles in this sauce and let them sit while you do the next step. They will start drinking it up.
Pound or chop the cracked peppercorns, garlic and cilantro roots together into a rough paste. A mortar is fastest, but a knife and the flat of the blade work fine.
Heat a heavy lidded pot or deep skillet (a Dutch oven is ideal) over medium heat. Add the neutral oil and the pepper garlic paste and fry for 1 minute until fragrant. Add half the ginger and fry 30 seconds more.
Lay the pork slices over the base of the pot in one layer. Pile the sauced noodles on top of the pork, pouring in any sauce left in the bowl. Scatter the remaining ginger and the celery over the noodles.
Arrange the shrimp on top in a single layer. Cover with the lid, turn the heat to medium low and cook for 8 minutes without lifting the lid. The steam trapped inside cooks the shrimp and finishes the noodles at the same time.
Lift the lid. The shrimp should be pink and curled and the noodles clear and glossy. If there is still a puddle of liquid at the bottom, cook uncovered for 1 to 2 minutes more. If the noodles look dry, splash in 2 tablespoons of water and cover for another minute.
Add the scallions, put the lid back on and turn off the heat. Rest 2 minutes. Toss everything together gently from the bottom so the pork and the pepper oil come up through the noodles. Finish with cilantro and serve with lime wedges and, if you like, a chili lime dipping sauce on the side.