This recipe contains some special ingredients unique to Thai cooking—galangal, lemongrass, Thai red chili, and Thai basil. Galangal is a rhizome related to ginger. While the flavour is similar to ginger, galangal is more pungent and peppery than ginger. Just as you would with ginger, remove the thin skin and then mince it before cooking. If you can't find galangal, ginger is an acceptable substitute.
Lemongrass adds a bright citrus note to the soup. Use only the light green bottom five inches or so of the lemongrass stalks where the flavour is concentrated. Choose stalks that are pale green and firm with a bulbous end. Sometimes you can find packages of pre-trimmed lemongrass. Trim the green tops and the hard end if not already trimmed. Before adding to the soup broth, bruise the lemongrass by crushing the stalks with a large rock or the side of a knife to release the aromatic oils. The soft inner leaves are edible, but remove the tough outer leaves before blending and serving. If you can't find lemongrass, leave it out and add extra lime juice before serving.
I used only one of the tiny Thai red chilis, also known as Bird's Eye Chilis, in this soup. With seeds and all, one chili is hot enough for me. Add more if so desired. Serrano chilis would also work.
Thai basil looks similar to sweet basil but has purple stems and flowers and a wonderful anise/licorice flavour. Sweet basil will not work as a substitute. If you can't find Thai basil, add a teaspoon or so of ground fennel seed along with the ground coriander.
Finally, I really like the texture of this soup when I let the sweet potatoes sit in the boiled water for 20 minutes before proceeding with the recipe. I find the soup is creamy and broth-like rather than thick and gloppy. As a bonus, the extra soaking time helps the flavours blend more. If you are short on time, you can skip this step and add the sweet potato, corn, and peppers at the same time, and carry on with the recipe.
makes 4-6 servings
1 small yellow onion, diced
2 cloves garlic, minced
2 1/2 cm/1 inch piece galangal or ginger, minced
1 to 3 small red Thai chilis, minced
4 stalks lemongrass
1 Tablespoon ground coriander seed
6 cups water
680 grams or 1-1/2 pounds yellow sweet potato, peeled and cubed
3 cups fresh or frozen corn
1/2 green pepper, diced
1/2 yellow pepper, diced
4 stalks cilantro, minced
1/4 cup Thai basil leaves, minced
lime juice, to taste
Trim the lemongrass and bruise it by pounding it with a rock or other heavy object and twisting it a bit. Cook the onion until translucent, adding a splash of water if needed. Add the minced garlic, galangal or ginger, red chilli, and ground coriander. Stir to combine. Add the lemongrass and 6 cups of water.
To your health and happiness,
Beans and Rice