In a clean wok or deep pan, add 2 tbsp oil and heat over medium high heat. Add the pickled mustard greens and cook for 2-3 minutes to dry it out a bit.
Push the pickled mustard greens to the side and add sliced garlic, ginger, green peppercorns, dried chilis, and pickled peppers. Stir fry for 2 minutes.
Pour in the fish broth and boil for 10 minutes.
Remove the pickled mustard greens and aromatics and transfer it to a serving plate or bowl.
Bring the remaining broth to a boil. Add the sliced fish and cook for 30 seconds to 1 minute.
Remove the cooked fish and place it on top of the pickled mustard greens. Carefully pour the broth over the fish.