Fish cooked sous-vide is moist and custardy. Too bad it’s a bit... dare I say it… boring. Fancy vocabulary aside, it’s poached fish, and that’s one cooking technique I am ambivalent about. Not that I don’t love the creamy sauces it produces, but the fish itself seems nothing more than a vehicle for sauce. But I don’t give up on an idea that fast. I’ve been experimenting with sous-vide fish on and off for a few years and finally have a dish that’s too good not to share. Here is what makes this work:
Halibut is extremely easy to dry out with conventional methods, so if you got your hands on a thick snowy white sparkling piece of halibut, this method shows off its texture like no other. Of course, there are other fish good choices, like striped bass or red snapper
I’ve seen temperatures for sous-vide fish from 104F to 140F and have tried almost all of them. For halibut, the magic number (for my taste) is 128F. Of course, at this temperature you are not killing either bacteria or parasites, so your halibut needs to be fresh (to deal with bacteria risk) and you need to be willing to take a tiny risk that it might contain parasites. Of course, even if it does, the odds of them making you sick are tiny.
The timing is crucial. No, you can’t keep things indefinitely in the water bath without changing the texture, and it is particularly true of fish. 15 minutes per inch at 128F works well.
I’ve tried cooking fish in zip lock bags with no additions, and with oil. Oil turned out to be very beneficial. It’s not just the temperature that counts, but heat capacity of the cooking medium. Oil transfers heat a lot slower than water and produces more supple results. Normally, you’d need a lot of oil to poach fish, but zip lock bags pack the oil very efficiently and let you get away with very little.
Since we’ll be cooking fish in oil, why not flavor it? I love a mixture of scallions, lemon zest and coriander seeds. Not only do I infuse the oil with them, but save them, crisp them up, and use as a topping. For the finishing touch, I broil halibut for just a minute with Dijon mustard butter. It was wasabi/sushi combination that inspired me to try it, and this topping was a definite keeper.
If you want to try this dish, here are the details.
2/3 cup (40g) scallions (green and pale green parts) cut into ½ inch lengths
1/2 tsp (1g) coriander seeds, crushed with a skillet
zest of 1 lemon removed with a coarse zester or peeled with a veg peeler and julienned.
Dry halibut, put into zip lock bags (1-2 pieces per bag), separating by thickness. Divide oil between bags. Submerge into a bowl of water to push out the air and seal. Cook at 128F for 15 min per inch.
2 tsp (10g) dijon mustard
Mix melted butter and mustard together with a fork. It will want to separate at first, but will come together after about a minute of mixing.
Eventually, it should look completely smooth.
Remove halibut from bags and place on a paper towel to catch the drips (do NOT dry the fish all over). Place in a broiler safe dish, top with a thin layer of mustard butter and pop very close to the broiler (about 2 inches away) to make it golden as fast as possible, 1 min tops. Or torch the top if you don’t have a gas broiler.
Divide the scallions / zest / coriander topping equally between fish pieces and serve.