Prep Vegetables: Dice sweet red peppers, regular red pepper, red onion, and white onion into small pieces. Cut ginger slices and green onion into smaller pieces.
Prepare the Fish: Use scissors to remove the pectoral and pelvic fins, trim off the dorsal fin, and make four to five angled cuts on each side of the fish. Sprinkle white pepper powder and season with salt all over the fish, including the cuts and inside.
Coat the Fish: Coat both sides of the fish with corn starch.
Pan Fry the Fish: Heat a wok on high, add oil, and carefully lower the fish in. Sear one side on medium-high heat for about 2 minutes to crisp up the skin. Flip and cook the other side for 2 minutes. Reduce heat to medium-low, splash with cooking wine, cover, and steam for 1 minute. Pan fry on medium heat for another 45 seconds.
Make the Sauce: In a clean wok, fry ginger, garlic, and shallots on medium heat until fragrant. Add the peppers and onions, cook for 40 seconds, then add a splash of cooking wine. Stir in the corn starch slurry, thin out with water if needed, and bring to a boil.
Serve: Transfer the fish onto a serving plate and pour the sauce over it right before serving.