Poaching wild-caught seafood is usually a matter of covering your seafood with your cooking liquid of choice — maybe milk, wine, stock, or olive oil — then heating everything up gently and slowly to produce a tender, luscious piece of seafood, cooked to perfection. If money is no object, or you’re just feeling extra fancy, you can also poach wild-caught seafood in butter, too.
While butter isn’t a liquid, per se, it’s an excellent poaching medium — and it is undeniably the most decadent. Butter-poached wild Alaskan fish and shellfish takes on all the flavors and the richness of this golden fat, creating a dish that you deserve to eat when you want to make something special. However, you’ll want to take extra care when you’re poaching with butter.
Why There’s a Subtle Art to Poaching in Butter
With butter, poaching is a bit more finicky, even compared to using another fat-based poaching medium like olive oil. Unlike poaching in olive oil, which is stable in its liquid form unless it’s exposed to high heat, butter is unstable at moderate temperatures.
Let’s walk through what happens when you’re melting butter in a pan over medium heat. Regardless of whether you’re using salted or unsalted butter, you might have noticed that there’s a point early on when, after the butter liquefies, it will begin to bubble. This is actually the moment that the butter is separating into molecules of fat, milk solids, and water. It might surprise you to learn that butter is not a stick of pure fat: It is actually an emulsion of water, fat, and milk solids, and this emulsion will break apart if it reaches a temperature of around 160 degrees F.
Poaching in Melted Butter
If you want to poach seafood in melted butter, you’ll need to keep the heat controlled and low, since you want to keep the butter from separating. It’s best to use an instant-read thermometer to help you try to dial in the temperature around 160 degrees. While seafood will still poach in butter that has separated, the milk solids will be floating on top of the fat as foamy bits rather than enveloping the seafood in rich, nutty flavors. Keeping the temperature low will prevent this separation from happening.
However, alternatively, you can bring the butter just to the point that it breaks, then pour it through a paper towel or cheesecloth to “clarify” it. This process of clarification removes the milk solids from the pan, leaving behind the fat and a bit of water; the flavor of your finished dish won’t be quite as rich, but your poaching medium will be much cleaner.
As an aside, clarifying your butter actually raises the smoke point of what’s left in the pan, since the milk solids are what burn at lower temperatures; this will come in handy if you want to reuse the clarified butter to pan sear your next seafood meal.
Aside from breaking the emulsion in butter, you’ll want to keep temperatures low enough to ensure that you’re poaching and not frying your seafood. If you hear any sizzling, turn down the heat; sizzling indicates that moisture is getting pulled from whatever is being poached, and you won’t have as silky a piece of seafood by the time it’s done.
Beurre Monté for the Most Luxurious Butter-Poached Seafood
Instead of using plain melted butter to poach seafood, you can create a more stable poaching liquid called beurre monté, a rich emulsion of butter and water that will give you a little more grace with the temperature of your pan. Beurre monté is often used to poach lobster, so it would be especially good for poaching spot prawns.
Beurre monté can still break apart, but it won’t do so until it is nearly boiling. When using it to poach seafood, you’ll want to keep temperatures around 180 degrees F; again, an instant-read thermometer can help you dial this in, but you won’t have to be as precise as you would when poaching with melted butter.
Another difference between melted butter and beurre monté is that the latter can be used as a sauce as well, delicious over seafood and any vegetables you have on your plate. Pouring plain melted butter over your seafood might seem like a sauce, but Julia Child would be very disappointed in you and encourage you to put in a little more effort.
How to Make Beurre Monté
The good news is beurre monté is incredibly easy to make. Mastering the French technique of making beurre monté will also make you feel like you’ve leveled up your domestic culinary game.
Like any proper French chef, you’ll need a whisk for this task.
The first thing you want to do is to cut a stick or two of cold butter into tablespoon-sized chunks — the total amount of butter that you use ultimately depends on how much poaching liquid you’ll need to go at least halfway up your seafood. Thinner cuts will obviously require less volume, but you can also choose a smaller pan that just fits what you’re trying to cook.
When you’ve chosen a pan that fits your choice of seafood, add a small amount of water to your pan and bring it to a simmer over low heat. You want about 1 tablespoon of water per stick of butter that you’re using, according to Chef Thomas Keller’s experience in this French technique.
Once the water begins to simmer, add in a piece of butter, whisking it in to incorporate the fat with the water. At no point should the water in your pan boil, as this will break apart the butter into fats, water, and milk solids. Keep things moving with your whisk, adding in one piece of butter at a time until you’ve incorporated everything to create a pale, yellow emulsion.
This emulsion is your beurre monté. You can use it immediately to poach seafood, to pour over your final dish as a sauce, or keep it in a warm place for a few hours as you would a hollandaise sauce — perhaps covered on the back of your stove, or even in a thermos. Beyond a few hours, the beurre monté will become unstable, so you might want to make just enough to use for your recipe.
However, if you have any left over, you can stash the beurre monté in the fridge for future use as melted butter. Keep in mind that any time you have butter left over from poaching, it will have picked up a faint flavor of wild-caught seafood along the way.
Get Poaching
You don’t have to follow a recipe when you’re butter-poaching wild-caught seafood; you can keep things plain, or simply add to your butter a sprig of fresh herbs or thin slivers of garlic, as their flavors will infuse gently into your seafood as it poaches. No matter how you decide to flavor your meal, make sure you’re seasoning your seafood before it goes into its butter bath.
As for how long poaching takes, it really depends on what you’re making and how thick it is. For fish, if you’re poaching a thin fillet, it can take under 10 minutes for it to get to a point where it flakes easily. For thicker fillets, it can take up to 20 minutes. If you’re poaching spot prawns, they’ll likely be done around the 5 minute mark, if not sooner.
If you’d like to use a recipe, try Hank Shaw’s recipe for butter poached seafood, using melted butter; it’s great for whatever fillet you have on hand, and would work nicely with spot prawns as well. Or check out Martha Stewart’s recipe for butter-poached spot prawns, which uses heavy cream to stabilize its poaching medium, instead of a pure beurre monté, for a truly decadent meal.
