Cod is a wonderful fish to poach because it keeps its shape and has a juicy interior; you could also use halibut (which is firmer), haddock (flakier), monkfish (very firm) or even seafood such as shrimp and scallops. I like the balance of sweet, salty, spicy and acid that comes from Thai seasoning. Add in eggplant rounds or zucchini if you like – be sure to sauté them at the beginning.