It’s very important to cut the vegetables very thinly. You can use a mandoline to slice all the vegetables and then a knife to cut the slices into matchsticks. You can use a knife if you don’t have a mandoline. If the vegetables are too large, they will not get a chance to cook through in the short amount of time that it takes the fish to cook. If you’d rather cut the vegetables larger, you will need to sauté them in a skillet first, to give the vegetables a head start in cooking, before placing the vegetables in the packets.
You can use any firm, thick fish fillets for this recipe. Salmon, cod, swai, tilapia, haddock, etc., it will all work here, as long as each fillet is about 6 oz. Don’t use fish that is thin, since it will overcook very quickly.