A quick brine before you cook prawns can make sure they're plump and juicy, no matter how you plan to cook them. You only need to let the prawnss sit in the brine for as little as fifteen minutes and you'll lock in moisture, add a little flavour and preserve a firm texture.
Image from carbonnyc.
Even if you're working with frozen prawns, you should still brine them. Serious Eats explains what the brining process does to your crustaceans:
Before we dive into the details, there's one technique that we've found improves all shrimp, regardless of cooking method: a quick brine of salt and baking soda. It may sound minor, but the combination works wonders: the salt helps keep the shrimp nice and moist as they cook, while alkaline baking soda delivers a crisp, firm texture.
Mix together one teaspoon of kosher salt and one quarter teaspoon of baking soda for every 500 grams of prawns you want to brine. Toss the prawns and brine together, then let them rest in the fridge for fifteen minutes to an hour. Then, cook them however you like. It's a simple tip that can apply to any of your favourite shrimp dishes, but if you need ideas, check out the full guide below.
Easy Techniques to Improve Any Shrimp Recipe [Serious Eats]