Thai Glass Noodle Soup: Ingredients and Preparation

Thai glass noodle soup is a light, aromatic broth with slippery transparent noodles, fresh vegetables, and savory toppings. The noodles, called woon sen, are made from mung bean starch and turn clear when cooked. The soup gets its flavor from a clear broth infused with garlic, cilantro roots, and white pepper, plus a balance of salty, sour, and spicy seasonings. This recipe takes about 30 minutes and serves 4.

What Are Glass Noodles (Woon Sen)?

Glass noodles, or woon sen in Thai, are thin, translucent strands made from mung bean starch and water. When dry, they look like brittle white or grayish threads, often sold in small bundles. After soaking and boiling, they become clear, soft, and slightly chewy with a slippery texture. Unlike wheat noodles, they have almost no flavor of their own, so they soak up the broth and seasonings around them.

You can find them in Asian grocery stores or online. They are not the same as rice vermicelli, which are white and made from rice flour, or cellophane noodles made from sweet potato starch, which are thicker and more elastic. For this soup, use thin mung bean glass noodles. If you cannot find them, thin rice vermicelli can work, but they will be less transparent and have a different bite.

Building the Clear Broth

The soup base is a clear broth, meaning it is not cloudy or creamy. You can use chicken stock, vegetable stock, or water with a little seasoning. The key is to infuse it with aromatics—ingredients that add fragrance and depth. In Thai cooking, the classic trio is garlic, cilantro roots (or stems), and white peppercorns, pounded into a paste or just simmered whole.

To make the broth fragrant, start by gently frying the garlic and cilantro roots in a little oil until they smell sweet and nutty. Then add your stock and bring it to a simmer. Add a splash of soy sauce or fish sauce for saltiness, and a pinch of sugar to round out the flavor. If you want a clearer, more delicate broth, avoid boiling it hard; a gentle simmer keeps it clean.

For a vegetarian version, use vegetable stock and replace fish sauce with soy sauce or mushroom seasoning. The flavor will be less deep but still aromatic.

Vegetables and Aromatics

Thai glass noodle soup often includes a mix of vegetables that add color, crunch, and nutrition. Common choices are:

• Napa cabbage or bok choy: Mild, slightly sweet leaves that wilt quickly in hot broth.
• Carrots: Thinly sliced or julienned for a touch of sweetness and orange color.
• Mushrooms: Straw mushrooms or shiitake add an earthy, meaty texture.
• Tomatoes: A few wedges give a little acidity and red color.
• Green onions and cilantro: Added at the end for freshness.

Feel free to use whatever vegetables you have; the soup is flexible. Just cut them into bite-sized pieces so they cook quickly. If you want more protein, add small shrimp, ground pork, or tofu.

Step-by-Step Preparation

Ingredients

• 4 oz (about 115 g) dried glass noodles (woon sen)
• 6 cups (1.4 L) chicken or vegetable stock
• 4 cloves garlic, minced
• 2 cilantro roots or 3 cilantro stems, chopped
• 1/2 tsp white peppercorns, crushed
• 2 tbsp fish sauce (or soy sauce for vegetarian)
• 1 tsp sugar
• 1 cup sliced mushrooms (straw or shiitake)
• 1 carrot, julienned or thinly sliced
• 2 cups napa cabbage or bok choy, chopped
• 1 tomato, cut into wedges
• Optional protein: 8 oz shrimp, ground pork, or tofu
• For serving: lime wedges, fresh cilantro, green onions, chili flakes or fresh chili, fried garlic (optional)

Steps

1. Soak the glass noodles in warm water for 10-15 minutes until soft and pliable. Drain and set aside. If the noodles are very long, cut them into shorter lengths with kitchen scissors.
2. In a large pot, heat 1 tablespoon of oil over medium heat. Add the garlic, cilantro roots, and white peppercorns. Stir-fry for 30-60 seconds until fragrant, but do not let the garlic brown too much.
3. Pour in the stock and bring to a gentle boil. Add fish sauce and sugar. Taste and adjust—it should be savory with a hint of sweetness.
4. If using ground pork or raw shrimp, add them now and let them cook for 2-3 minutes. For tofu, add it with the vegetables.
5. Add the mushrooms, carrot, and tomato. Simmer for 2 minutes.
6. Add the cabbage or bok choy and the soaked noodles. Cook for 2-3 minutes until the noodles are completely transparent and the vegetables are tender but still bright.
7. Turn off the heat. Ladle the soup into bowls and top with fresh cilantro, green onions, and a squeeze of lime juice. Serve with chili flakes or fresh sliced chilies on the side.

Seasoning Your Bowl

Thai soups are often seasoned at the table with four flavors: salty (fish sauce), sour (lime juice), sweet (sugar), and spicy (dried chili flakes or fresh chilies). For glass noodle soup, the broth already contains fish sauce and sugar, but a final squeeze of lime brightens the whole dish. If you like heat, add a pinch of chili flakes or a few slices of fresh Thai bird's eye chilies. A sprinkle of fried garlic adds a crispy, nutty finish.

Comparison: Glass Noodles vs. Other Noodles

Glass noodles are unique because they become nearly invisible in broth, letting the colorful vegetables and aromatics stand out while adding a delightful slip-and-chew texture.

Serving and Storage

Serve the soup immediately, as glass noodles continue to absorb liquid and can become overly soft if left too long. If you plan to have leftovers, store the broth and noodles separately: keep the cooked noodles in a little water or oil to prevent sticking, and add them to the reheated broth just before serving. The broth can be refrigerated for up to 3 days.