Prik Gaeng Khiao Waan (Thai Green Curry Paste)

For many Americans, green curry, or gaeng khiao waan, has become synonymous with Thai cuisine, so much so that if a Thai restaurant didn’t have a green curry prominently featured on the menu, most people would eye the kitchen with suspicion. Likewise, if you’re a fan of Thai food and you like cooking, you probably have a can of green curry paste in your pantry right now, or know where you can find some easily, since prepared Thai curry pastes are quite easy to find at well-stocked grocery stores, Asian markets, and, of course, online.

Why You Should Make Your Own Green Curry Paste

The fact that green curry and prepared green curry pastes are easy to find might make you think there’s no reason to make green curry paste from scratch at home. However, I think that because green curry is so familiar to so many, making your own green curry paste, or prik gaeng khiao waan, can clearly illustrate why and how scratch-made curry pastes are superior to prepared versions, provided you prepare them with an eye toward proper technique and seasoning. A freshly made prik gaeng is intensely aromatic because of the pounded ingredients, and you’re able to easily pick out each component—the fruitiness and pungency of fresh chiles and alliums, the floral and herbal notes of lemongrass and galangal, the heady depth of ground spices, and the savory punch of shrimp paste. A canned curry paste doesn't have any of the brightness and nuance of a fresh paste, and the flavors of each component are muted and muddy in comparison. Making green curry paste also offers a few lessons in ingredient substitution, and necessitates careful consideration of how and in what order you combine ingredients in a mortar and pestle.

The main ingredients for prik gaeng khiao waan are relatively easy to find and frequently used in a wide variety of curry pastes: chiles, lemongrass, galangal, makrut lime zest, coriander root, garlic, shallots, dried spices, and shrimp paste. For example, the only difference between a green curry paste and a basic red curry paste (prik gaeng phet) is the color of the chiles used (red curry paste is made with dried red chiles rather than fresh green ones). 

Choosing the Chiles

In Thailand, green curry paste is made with a variety of green chiles, the most common being  prik kee noo suan khiao, a small, spicy green chile that's hard to source in the US; prik cheefa khiao, a large, green spur chile that sits on the milder side of the heat index spectrum; and prik jinda khiao, the skinnier, smaller, spicy green peppers known in the US as “Thai chiles.” The combination provides a balance between the fruity and the fiery notes of fresh chiles, while also lending the paste its distinctive pale green hue.

Making a green curry paste in the US requires that you get a little creative with chile substitution, since many varieties of fresh Thai chiles can be hard to find. Serrano chiles work well as a like-for-like substitution for spur chiles, but if you have access to a Korean market, such as HMart, I’ve also had success using a combination of mild (asagi gochu) and spicy (cheong-yang gochu) Korean green chiles. The goal with any chile substitution is to provide the paste with its color, the fruity aroma and flavor of a fresh pepper, and to ensure that the chile paste is sufficiently but not overpoweringly spicy. 

Tips for Working With a Mortar and Pestle

The high moisture content of fresh chiles makes green curry paste one of the trickiest Thai curry pastes to pound by hand in a mortar and pestle. As the chiles break down in the mortar they release water, which makes it harder to generate the abrasive friction between the pestle and mortar that’s required to pound the more fibrous ingredients into a fine paste.

There are a few tricks and tips that can make this process easier. The first is to make sure the ground spices and salt in the recipe are already in the mortar when you start pounding the chiles so they can absorb some of the liquid; it’s common with other curry paste preparations to add them later. I also recommend that in the initial stages of pounding the fresh chiles you keep the pestle as close as possible to the ingredients while pounding, so you don’t have chile juice and shrapnel splashing in your eyes (trust me, it isn’t pleasant).

Once the chiles are broken down into a paste, you can start lifting the pestle higher to pound with more force from a greater height, although you should make sure to use the sides of the mortar to help break down ingredients—while pounding in the center of the bowl is definitely called for, it is the friction created by the pestle rubbing against the mortar’s walls that does most of the work in breaking up the ingredients. Finally, thinly slicing the aromatics that go into the paste—particularly fibrous galangal and lemongrass—significantly speeds up the process. The ingredients have to get broken down at some point, and taking the time to (carefully) slice them beforehand will save you a lot of time and effort.

Scaling Up

This recipe produces roughly four ounces (1/2 cup) of curry paste, which is the equivalent of one can of store-bought paste. I decided on this quantity because if you want to make green curry using my green curry recipe but don’t feel like making curry paste from scratch, you can easily substitute a store-bought paste. But the relatively small quantity of paste this recipe produces means that it can’t be made easily in a standard-sized food processor or blender: The volume of ingredients is too small to be processed properly, and much of it will just get stuck to the sides of the blender jar or processor bowl without getting pulverized.

However, if you want to scale up the recipe to make a much larger batch of paste, the high moisture content of the chiles will work to your advantage, as it makes it easy to purée the ingredients in a blender. The paste can then be divided into four-ounce portions and frozen for months. That said, I do recommend making this recipe in a mortar and pestle to get a feel for the process and the desired texture of the paste. With a little practice, pounding a curry paste doesn’t take all that much effort, especially if you follow some basic technique principles.

• Make sure to thinly slice the fresh aromatics before adding them to the mortar; smaller pieces are much easier to process into a paste.
• Add only one ingredient at a time to the mortar (because of the small quantities and comparable texture, shallots and garlic can be added at the same time), and don't move on to the next one until you have fully pulverized the latest addition; overcrowding the mortar will just slow you down and make a mess.
• Use the weight of the pestle to your advantage; start by simply tapping the ingredients with the heavy pestle to crush them, and then move on to more energetic pounding.
• Embrace the process; once you get the paste going, it becomes easier to incorporate each subsequent ingredient.
• Give yourself some arm relief by grinding whole spices separately in a spice grinder before incorporating them into the paste in the mortar and pestle.