Make a ¼-inch deep cut down the entire back of each shrimp. Rinse, drain, and pat dry with a paper towel. Prepare all of your vegetables—the bok choy, snow peas, mushrooms, bamboo shoots, and water chestnuts—and have them ready before you start cooking.
Premix the sauce by combining the chicken stock, oyster sauce, Shaoxing wine, light soy sauce, dark soy sauce, sugar, sesame oil, white pepper.
In a wok or small pot, heat 2 to 3 cups of canola oil to 325°F/160°C. You’ll fry the shrimp in 2 to 3 batches. Make the dry mix for the batter by combining the all-purpose flour, salt, baking powder, onion powder, garlic powder, and white pepper. Right before frying, mix dry ingredients with seltzer to form your batter.
Place the shrimp into the batter to fully coat. Carefully lift each shrimp out of the batter, letting any excess drip off. Quickly, carefully place each shrimp into the hot oil. Increase the heat as needed to keep the oil temperature at 325°F/160°C. Gently move the shrimp around until light golden, about 2 minutes. Repeat with the remaining shrimp, and let all of the shrimp rest for about 5 minutes.
Meanwhile, bring a medium pot of water to a boil, and add the bok choy, mushrooms, bamboo shoots, and water chestnuts. After 20 seconds, stir in the snow peas. Then use a strainer to lift everything out onto a plate.
Next, bring the frying oil back up to 350°F/177°C, and re-fry the shrimp in 1-2 batches until crispy and golden brown. Set aside and start right in to making your sauce because you don’t want the shrimp to sit very long after the second fry.
Use a spider or larger strainer to remove the shrimp from the oil. Heat the wok to just smoking, and add 1 tablespoon of the frying oil. Stir in the chopped garlic. Immediately pour in your sauce mixture, and bring it to a boil. Stir up your cornstarch slurry mixture, and stir it into the sauce.
Toss in the blanched vegetables until they are coated with sauce and heated through. This takes about 20 seconds, and the sauce should be bubbling. Turn off the heat, add the fried shrimp, and gently toss a few times. The shrimp doesn’t need to be completely coated in sauce (giving you both crispy and saucy textures in the dish). Plate and serve immediately!