Why they’re so good!

Butterflied prawns doused in a Thai style lime, chilli and garlic dressing then grilled to tender, juicy perfection. They make the perfect seafood starter or meal and they’re so easy to make.

The prawns (shrimp) can be prepared the day before cooking then take just minutes under a broiler/overhead grill. Or you could even get out in the sunshine and cook them on the BBQ.

The dressing is robust and absolutely delicious and these crowd-pleasing prawns are great served on their own as a party appetiser or add some rice and a green salad or Thai salad on the side. So, so good!

Top down view of prawns on a large platter with a bowl of dressing.

Ingredients you’ll need

Ingredients for nam jim prawns on a baking sheet.

Jump to the recipe for full ingredients and instructions.

  • Prawns: The larger your prawns or shrimp, the better. You’ll just need to adjust the amount of grilling time according to size. I use XXL tiger prawns here which are about 13-16 prawns per 500g (13-14 per 1lb). King prawns would also be great and if you can get jumbo size go for it. You might want to just do 20 if using jumbos.
  • Chilli: There are two types of chilli in the dressing – one long red chilli and some dried chilli flakes (red pepper flakes).
  • Lime: Use fresh lime juice for the best flavour here. It adds an irresistible tang. Lemon juice will work fine if you have that on hand but it will give a different flavour, obviously.
  • Garlic: Use fresh garlic cloves and mince them in a garlic crusher or just chop them super fine.
  • Oil: Use a neutral flavoured vegetable oil here.
  • Fish sauce: A classic in Thai cooking use a good quality fish sauce (I use Squid brand).
  • Sugar: Some white sugar, or traditionally palm sugar, is used to sweeten the sauce.
  • Coriander/Cilantro: There’s just a little fresh coriander in the dressing and I love to garnish the prawns with some too.
butterflied prawns on top of a salad.

How to make butterflied prawns

So why butterfly prawns anyway? Prawns cooked in the shell have so much more flavour so cooking them this way makes them taste amazing but keeps the flesh easy to get to and you can get the dressing right into the meat. It really is a lovely way to serve prawns. While you can generally pull the meat out with a fork, have some napkins on hand as they might get a bit sticky.

There is a little time in preparation, as there always is with prawns but it takes me about 20 minutes to prep them and it can be done ahead. You can also take a shortcut too, by cutting the heads off so you don’t need to clean them

Jump to the recipe for full ingredients and instructions.

1. How to butterfly prawns

First up, please be careful. The shells can be slippery and you don’t want your knife to slip so don’t rush this step. I tested a few different methods and I found this one to be the safest to me.

Place the prawn belly side down on a chopping board (while some people butterfly them through the belly, I find they slip around too much because the back isn’t flat). Using a serrated sharp knife, with just light pressure, start to saw along the roundest part of the back.

Showing how to slice a prawn.

Once you’ve got part of the shell cut through to the meat, make sure your knife is lined up straight along the centre of the prawn and, with one hand holding the knife and the other on top, press straight down.

Cutting straight down on the prawn.

Open it up, and press it down flat so you have a perfectly butterflied prawn.

A single butterflied prawn on a chopping board.

2. Clean the prawns

Pull out and discard the digestive tract, then carefully rinse the heads. If you don’t feel like cleaning the heads, you can just slice them off. Unless your a person who loves eating prawn heads they really aren’t there for any reason other than aesthetics.

3. The nam jim dressing

Chop your chilli and garlic as fine as you can (traditionally they’d both be pounded together in a mortar and pestle), then simply add the nam jim ingredients to a glass jar with a tight-fitting lid and give it a good shake to mix and dissolve the sugar.

The nam jim dressing in a glass bowl.

4. Dress the prawns

In a large bowl add the oil, salt and ¼ cup of your dressing. Add the prawns and give it all a good but gentle toss, making sure to open up the prawns and get the dressing all over the meat (they’ll naturally close up into their normal shape as you mix them). It doesn’t matter if they break apart.

The dressed prawns in a bowl ready to cook.

5. Grill the prawns

Lay the prawns out on a baking sheet lined with foil, meat side up and drizzle over any dressing that’s dropped to the bottom of the bowl – definitely don’t let it go to waste. Simply place the prawns under a broiler/overhead grill for 3 ½ minutes. This time is for the XXL size that I use you may need to adjust if your prawns are larger or smaller. They’re done when the meat is fully opaque but should still be juicy, not dry.

12 prawns laid out on a baking sheet ready to cook.

How to serve butterflied prawns

These are great served up share style on a nice big platter and don’t forget to drizzle over a little more nam jim, then leave the rest on the side for people to add what they like to their own prawns.

While you can pull the prawn flesh out with a fork, you’ll probably need to hold it with your other hand, so have some napkins on standby.

I love serving these as an appetiser as much as I love to serve them as a full dinner. For dinner, I add some simple steamed rice and a Thai salad (really just a green salad with lots of herbs like mint, coriander/cilantro and Thai basil – treat the herbs like a salad leaf, in other words, don’t skimp and leave them whole).

Dressing being spooned over butterfly prawns.

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A batch of butterflied prawns on a platter with a small bowl of dressing.
5 from 2 ratings
These butterflied prawns take just minutes to cook and are dressed in a flavourful nam jim dressing. These juicy grilled prawns are a great starter or a meal.


  • 24 shell-on XXL tiger prawns any size fine, cooking time will vary
  • 1 teaspoon fine sea salt / kosher salt
  • ¼ cup neutral flavoured vegetable oil


  • 1 long red chilli finely chopped with or without seeds
  • 4 cloves garlic minced
  • ½ teaspoon hot dried chilli flakes (or 2-4 birdseye chilli to taste)
  • ¼ cup lime juice (2-3 limes)
  • ¼ cup white sugar
  • 2 tablespoons fish sauce
  • 1 tablespoon finely chopped coriander (cilantro)


  • lime wedges
  • Fresh coriander/cilantro

For best results, always weigh ingredients where a weight is provided


  • 2 Large baking sheets


  • In a mason jar combine the nam jim dressing ingredients and shake well to combine. Set aside.
  • The safest way I’ve found to butterfly prawns is the lay them flat on their belly and press down a little. Holding each side of the prawn with one hand, with a serrated knife in the other hand, very carefully start to cut along the back of the prawn where it humps up a little. Once you’ve cut through the top part of the shell, making sure the knife is in line right down the centre of the head, back and tail press down to slice it in half. Repeat with all the prawns.
  • Remove the digestive tract and gently rinse the heads clean. You can cut the heads away if you prefer.
  • Transfer the prawns to a large bowl with the oil, salt and ¼ cup of the dressing. Toss to coat evenly trying to make sure to get the meat side well coated. Set aside remaining nam Jim for serving.
  • Preheat overhead grill / broiler to high and have a rack about 6 inches below.
  • Place the prawns onto a baking sheet meat side up. You can fit about 12-14 onto one large sheet so if you have a second, prep that while the first batch are in the oven. As you take them from the bowl, open each one up and dip in any dressing that’s sunk to the bottom of the bowl so you don’t leave any behind. Grill/broil for 3-4 minutes until just cooked. The size of the prawns will determine how long they take to cook but it’s easy to tell when they’re done – the meat will be opaque white.
  • Transfer to a platter. Serve with coriander leaves and wedges of lime for squeezing over and the remaining nam Jim sauce.
  • Please take a moment to leave a comment & rating. It's appreciated and so helpful.


  1. Tablespoons: I use a standard Australian 20ml tablespoon (equal to 4 teaspoons). Check yours before measuring.
  2. Prawns: I used the XXL tiger prawns which are about 13-15 per 500g/1.1lb. You can use any type of prawns/shrimp but the large ones are easier to butterfly cut. King prawns work great too. Jumbo prawns would be fantastic and meaty. The size of your prawns/shrimp will dictate the time required for cooking.
  3. You can also cook them on a BBQ. Preheat to medium-high, then grill meat side down for 2-3 minutes, flip and grill a further 1-2 minutes.
  4. Serves 4 as a meal or 6-7 as an appetiser.
  5. Nutrition details are approximate only – scroll below the recipe to find the full nutritional information.
Have you tried this recipe?Don’t forget to leave a rating and comment below and let me know how it was! I love hearing from you. Nutrition information is approximate and derived from an online calculator. The brands you use may cause variations.
Nutrition Facts
Butterflied Prawns (with Nam Jim Dressing)
Amount Per Serving
Calories 317 Calories from Fat 144
% Daily Value*
Fat 16g25%
Saturated Fat 2g13%
Trans Fat 0.01g
Polyunsaturated Fat 2g
Monounsaturated Fat 10g
Cholesterol 236mg79%
Sodium 2355mg102%
Potassium 310mg9%
Carbohydrates 18g6%
Fiber 0.4g2%
Sugar 14g16%
Protein 26g52%
Vitamin A 534IU11%
Vitamin C 22mg27%
Calcium 116mg12%
Iron 1mg6%
* Percent Daily Values are based on a 2000 calorie diet.