Season the shrimp with ¼ teaspoon kosher salt and ⅛ teaspoon of the white pepper. Set aside.

Stir the soy sauce, oyster sauce, sugar and remaining ⅛ teaspoon white pepper together in a small bowl until the sugar dissolves. Set aside.

Heat a large wok over medium-high heat until it starts to smoke. Swirl in 1 tablespoon oil to coat the wok. Add the shrimp and sear on one side until golden brown, about 1 minute, then stir-fry until cooked through, 1 to 2 minutes longer. Transfer to a plate and set aside.

Swirl 1 tablespoon neutral oil into the wok and return it to medium-high heat. Spread about half of the coleslaw mix in an even layer over the wok and cook until the coleslaw browns, 1 to 2 minutes. Transfer to the plate with the shrimp. Heat the remaining 1 tablespoon oil in the wok and sear the shiitake mushrooms until golden brown, 2 to 3 minutes. Add the ginger and garlic and stir-fry until fragrant, about 30 seconds. Add the shrimp, charred coleslaw, remaining half of the coleslaw mix, shredded carrots and brown rice to the wok and stir-fry until evenly combined.

Drizzle the soy sauce mixture around the edges of the rice along the sides of the wok and toss until evenly distributed. Let sit until the rice starts to brown, about 1 minute. Toss to evenly combine the brown bits.

Divide the rice among 6 bowls, sprinkle evenly with chopped scallions and garnish with 1 teaspoon Chinese hot mustard per bowl.