To make the sauce, in a bowl, combine the hot water and sugar. Whisk until the sugar dissolves. Add the soy sauce, dark soy sauce, oyster sauce, and sesame oil. Mix well and set aside.
To marinate the shrimp, in a bowl, combine the salt, white pepper, rice wine, sesame oil, cornstarch, and water. Add the shrimp and toss gently to coat. Marinate for 10 minutes, then transfer the shrimp to a plate in a single layer.
To steam the shrimp, bring a steamer to a boil over high heat. Place the shrimp in the steamer, cover, and steam for about 2 minutes until cooked through. Remove and set aside.
To prepare the Cheung Fun batter, in a bowl, whisk together the rice flour, tapioca starch, wheat starch, and water until smooth.
To steam the Cheung Fun, brush about 1 teaspoon of avocado oil into a heat-resistant container. Whisk the batter again, then pour about ½ cup into the container. Place it into a steamer over high heat and steam for about 4 minutes until set. Remove and let cool for about 2 minutes. Repeat with the remaining batter, whisking before each batch.
To assemble the rolls, lightly oil a work surface. Place 3 to 4 shrimp evenly across a rice noodle sheet. Using a plastic scraper, carefully roll the noodle sheet over the shrimp. Transfer to the work surface and trim the two edges if desired. Repeat with the remaining noodle sheets and shrimp.
To serve, arrange the Shrimp Cheung Fun on a serving plate. Drizzle with the sauce and serve immediately.