If using a whole fish, score the thickest part of the fish with a few diagonal lashes on both sides. Rub the fish (both the outside and inside) with the salt and wine. Place the ginger in its cavity. Set aside for several minutes while you prepare all other ingredients.
Heat a generous amount of oil in a wok or a shallow frying pan over medium heat. Once the oil is hot, pat the fish dry and add it to the pan. Increase the heat as needed and fry until both sides are golden, about 2 minutes each side depending on its thickness. There is no need to cook it all the way through. Transfer the fish to a plate and remove the frying oil from the pan.
Add some oil to lightly coat the bottom of the pan and heat it over medium heat. Then add minced ginger and sauté for a minute until fragrant. Then add diced onions and continue to cook for about 45 seconds. Then add the white parts of scallions and minced garlic to the pan and cook briefly until fragrant.
Add Lao Gan Ma sauce to the pan and continue to stir and cook until you can smell the fragrance, about a minute. Add both types of soy sauce, sugar and ½ cup (120ml) of water to the pan. Give everything a stir and let it come to a boil.
Slide the fish into the pan and reduce the heat to a simmer. Cover the pan and braise each side over low heat for 5-8 minutes, depending on its thickness and how much flavor you want it to soak up.
Carefully transfer the fish to a serving plate. Turn the heat to medium and taste the sauce and adjust the seasonings if needed. If too much liquid has evaporated, you can also add a splash of water to the sauce. Stir the cornstarch with 1 teaspoon of water. Slowly add the cornstarch slurry while stirring to thicken the sauce to your liking.
Throw in diced chili pepper and green parts of scallions. Stir the sauce one more time then turn off the heat. Pour it over the braised fish and serve right away.