Khao Soi (or kao soi) is a curry noodle soup from Northern Thailand and is often recommended as one of the key dishes visitors must try when traveling to Chiang Mai. It is heavily influenced by neighboring China and Myanmar, featuring ginger and soy sauce (China) as well as black cardamom and fresh turmeric (Myanmar). Northern Thai food is the mildest in Thailand which makes this a great dish for kids and those of us who are more spice averse.
This dish lends itself well to veganization because it doesn't rely on fish sauce for seasoning, and instead calls for soy sauce. This is a big help, as the fish sauce in Thai curries is a really tricky ingredient to replace. You can make a swap for a very light soy sauce in a red curry for example, but it will taste quite different from the standard recipe using fish sauce.
This recipe employs a bit of a shortcut. I've developed it using a store bought curry paste, because I think it's a great idea to find new ways to use a red curry paste beyond a simple red curry. The most common size for a tub of Thai curry paste is 14oz, which yields around 50+ servings. So once you've used a paste for a recipe, you'll have to freeze the remaining paste for future use. You can definitely make red curry 50 more times, but wouldn't it be fun to make other dishes with the past in your freezer? In any case, this recipe translates beautifully for vegans, so let's get into it!
Special Ingredients for This Curry
To me, black cardamom smells exactly like BBQ sauce - indistinguishable! For Khao Soi, it's perhaps the most important spice in the recipe. The smoky aroma permeates the dish and sets it apart from any Thai curry you've had before. Needless to say, black cardamom it is essential and unfortunately can't simply be substituted for its green counterpart. Green cardamom lacks a smokey aroma, so it doesn't do the trick on its own. If you twisted my arm, I'd guess you could substitute with a 50% reduced amount of green cardamom plus a drop or 2 of liquid smoke might get you there. But black cardamom isn't impossible to find, so do try to seek it out! I bought mine from Oaktown Spice shop, and have also seen it at 99 Ranch and even on Amazon. The Spruce Eats wrote a lovely comprehensive article on black cardamom, which I highly recommend reading!.
Fresh or dry powder turmeric is another key and somewhat unique ingredient in this curry. The traditional recipe calls for fresh, but I've had a lot of success using dry.
Ginger is quite a unique recipe in a Thai curry. Traditionally the fresh root is pounded into the paste, but I've also had success simmering slices of fresh ginger in the soup to infuse it's flavor and aroma, when I'm doctoring up a store bought paste.
Soy Sauce is the salty seasoning traditionally called for in this recipe, which is why it's so easily made vegan compared to other Thai curries which rely on fish sauce for salt. Use a Thai soy sauce when you can. They are much lighter in flavor and aroma compared to Chinese and Japanese soy sauces. If you can't find Thai brands, use a low sodium variety from Kikomon. See my Thai ingredients post for more on which soy sauce to choose for Thai cooking.
Noodles in this dish show up in two ways. They are boiled in salted water and then added to individual bowls for serving, and they're also deep fried and used as a crispy topping. I've elected not to deep fry the noodles in my recipe mainly because I don't like to deep fry and I think the dish is delicious without them.
Sourcing noodles for the dish is pretty flexible. Today in Thailand you will find Khao Soi served with fresh egg noodles (aka wonton noodles) which are easy to find in Asian / Chinese grocery stores. I've actually had success using flat dried Italian pasta like linguini (don't tell my Thai friends!), and you could use fresh linguini as well. As the name would suggest, Khao Soi originally used rice noodles, as khao soi is the Burmese phrase for cut rice. So a medium sized flat rice noodle is a perfectly fine, and maybe even more traditional choice than the wonton style egg noodles used in Thailand today.
If you want to be super restaurant style authentic, and fry some of your noodles for a crispy topping, it's easiest to use a fresh egg noodle or a rice vermicelli as you can fry them straight from the package. If you're using a dried pasta, you will have to boil and thoroughly dry the cooked pasta before frying. Here's a post about frying Thai vermicelli and another about frying egg noodles.
How do you make Khao Soi Vegan?
There are two places where animal products need to be removed from this recipe. The first place is the protein (normally chicken) used to make the broth of the soup, and as the main protein in the soup. This was an easy swap as my famous chickpea broth is an excellent substitute for chicken stock. Instead of chicken meat in the soup, we're using chickpeas and some nice fat chunks of tofu.
The second place only applies when you're using a store bought curry paste as your base, rather than making the paste from scratch and that is to ensure you have a curry paste made without shrimp paste. After reading the ingredients on the Aroy D curry pastes, I noticed that their pastes generally don't contain shrimp paste. So for vegan recipes, Aroy D is the curry paste to go with! It is available on Amazon, and I've found it at 99 Ranch, but it will depend on your store, your local Asian market might sell the Mae Ploy brand which aren't vegan. It will come in 14 oz tubs (freeze after opening!), but sometimes you can find it in 50g packs, which are great for single recipe use.
Vegan Khao Soi Ingredients
40-50 grams / 4 T Aroy D Red Curry Paste
1 T turmeric powder OR 2 T fresh turmeric paste (microplane or mortar and pestle)
3 large black cardamom pods
2 t whole coriander seed
10 slices of ginger root (peeled)
1 t sea salt
4 cups water
1/2 cup dried chickpeas (must be dried - this is how we build the broth)
1 T Thai soy sauce
1 T cooking oil
1.5 cup Aroy D Coconut Milk (boxed if you can)
1 cup tofu, cut into 1 inch cubes
Pickled Mustard Greens or (quick sub - sautéed greens seasoned with vinegar)
Khao Soi Recipe Method
The day before, soak your chickpeas overnight is salted water: 1/2 cup dried chickpeas, 4 cups of water, 2 teaspoons kosher salt.
Add your soaked chickpeas to a pot with 5 cups of water and 2 teaspoons kosher salt, bring this to a boil and then reduce to a simmer. Check them once in a while and skim the foam if you’re so inclined. If they are relatively fresh chickpeas, it will likely take 30-40 minutes to cook. Set a timer for 30 minutes as a reminder to check the chickpeas for doneness. If they are cooked before you finish the with curry paste prep, just turn off the heat and come back to them later.
To elevate the aroma of this dish, we will start by lightly toasting the warm spices. Using your mortar and pestle (M/P - you should really get one if you don't have one yet!) lightly tap the black cardamom pods to crack open their hard shell. Remove the small seeds inside and drop them in a dry pan. Bring the heat to medium and toast them in the pan until they're very aromatic. When they're ready, drop them back into your mortar and let them cool for a minute. Next, add you coriander seeds to the pan and similarly toast until aromatic - then drop them in the mortar. Next, (for extra credit) drop your ginger slices into the dry pan and toast them a bit, until they are slightly black on the edges.
Grind up your dry spices in your M/P into as fine a powder as you can manage. Add in the ginger slices and pound them into a paste.
Have your measured 1.5 cups of coconut milk ready.
Measure out your Aroy D curry paste into a small bowl and add in your ginger spice paste, 1T turmeric powder and 4 T of coconut milk (drawing from the measured 1.5 cup), mix this until well combined.
Next, cook the curry paste. In a nonstick sauté pan, add 1 tablespoon cooking oil and your curry paste coconut milk mixture. Turn the heat to medium and cook this until the edges of the paste are collecting with oil and curry aroma fills your kitchen. As water evaporates from the paste, the pan may become dry which can and cause the paste to burn. Have your measured coconut milk on hand to add a little, bit by bit to the pan (about 2T at a time) to loosen your paste and keep it from burning in the pan. When you see red oil separating from the paste, and your kitchen smells really aromatic, you're ready for the next step!
The next step is the add all of remaining coconut milk to the pan and mix it well with the paste. Next, you transfer this to your pot of chickpeas. The water you’ve cooked your chickpeas in is the base for your broth, so don’t drain the chickpeas! Next, add the tofu and season with soy sauce. If your chickpeas are still undercooked, simmer this until they are tender.
Put some heavily salted water on the stove and bring it to a boil, use a pot large enough to accommodate your pasta and allow it to freely move around the water as it boils. Cook the pasta or noodles according to the package instructions. When the noodles are cooked, add the directly to serving bowls and get to plating!
To serve: Place a generous amount of noodles in a soup bowl. Pour the broth into the bowl and top with chickpeas and tofu. Prepare a condiment dish of limes wedges, sliced shallots, chili flakes and pickled mustard greens. Enjoy with a friend!