How to Make Gaeng Liang: Thai Peppery Vegetable Soup with Hairy Basil

Gaeng Liang is the sort of Thai dish that shows how much flavour can come from a light, clear broth. It is packed with vegetables and prawns, but what makes it distinctive is the peppery seasoning paste and a generous handful of fresh Hairy Basil added right at the end.

You may also see the name written as Kaeng Liang or Gang Liang. Whichever spelling you use, this is a warming, aromatic soup with no coconut milk and no need for a ready-made curry paste. The seasoning is made from a few characteristic Thai ingredients, including peppercorns, dried shrimp, shrimp paste and fresh fingerroot.

This recipe serves four and is easy to adapt to the vegetables you have available.

What is Gaeng Liang?

Gaeng Liang is a traditional Thai vegetable soup with a savoury, peppery broth. Unlike a rich coconut curry, it is light and brothy. Its warmth comes mainly from peppercorns and aromatic fingerroot, while fresh chillies are optional.

The exact selection of vegetables varies. Pumpkin or squash, baby corn, mushrooms and angled luffa are all common choices. Courgette works well when luffa is not available. Prawns add sweetness and substance, while dried shrimp and shrimp paste build depth in the broth.

The final ingredient is especially important: Hairy Basil, known in Thai as bai maenglak and sometimes written bai meng rak. Its bright, lightly lemony and gently peppery flavour gives Gaeng Liang its recognisable finish.

If the different Thai basil varieties are still a little confusing, read our guide to Holy Basil, Sweet Basil and Hairy Basil before you begin.

Why Hairy Basil matters in Gaeng Liang

Fresh Hairy Basil is not simply a garnish in this recipe. It is stirred into the hot soup after the pan comes off the heat, so its fresh citrusy aroma perfumes the whole broth without the leaves being overcooked.

Lemon basil is the closest substitute if you genuinely cannot find Hairy Basil. Thai sweet basil can be used in an emergency, but its sweeter aniseed character will change the flavour of the dish. Holy basil is more peppery and does not provide the same lemony lift.

Gaeng Liang recipe

Serves: 4
Preparation time: 25 minutes
Cooking time: 20 minutes

For the seasoning paste

• 25g dried shrimp, soaked in warm water for 10 minutes and drained
• 1 teaspoon white or black peppercorns
• 4 red shallots, peeled and roughly chopped
• 20g fresh fingerroot, thinly sliced
• 1 tablespoon shrimp paste
• 1–2 Thai bird's-eye chillies, optional

For the soup

• 1.2 litres water or unsalted stock
• 250g pumpkin or butternut squash, peeled and cut into 2cm pieces
• 150g baby corn, halved lengthways
• 1 medium courgette or angled luffa, cut into bite-sized pieces
• 150g oyster mushrooms, torn into pieces
• 250g raw peeled and deveined prawns
• 2 tablespoons fish sauce, plus more if needed
• 1 teaspoon palm sugar, optional
• 1 large handful fresh Hairy Basil, leaves picked from the thicker stems
• Steamed jasmine rice, to serve

Allergen note: This recipe contains crustaceans and fish. Some shrimp pastes may contain additional allergens, so always check the label.

1. Make the paste

Using a mortar and pestle, pound the drained dried shrimp and peppercorns until broken down. Add the shallots, fingerroot and chillies, if using, then continue pounding to a rough paste. Work in the shrimp paste last.

A small food processor can be used instead. Add a spoonful of water only if needed to help the blades move; the paste does not have to be completely smooth.

2. Start the broth

Bring the water or stock to a gentle boil in a large saucepan. Add the seasoning paste and stir well to disperse it through the liquid. Simmer for 3–5 minutes, until the broth smells fragrant and the shallot no longer tastes raw.

3. Add the vegetables in stages

Add the pumpkin first and simmer for about 5 minutes. Add the baby corn and cook for another 2–3 minutes, followed by the courgette or luffa and the oyster mushrooms.

Continue cooking gently until the vegetables are tender but still hold their shape. Avoid a fierce boil, which can break up the pumpkin and make the broth cloudy.

4. Cook the prawns and season

Add the prawns and simmer just until they are firm, opaque and cooked through, following the packet instructions. Stir in 2 tablespoons of fish sauce. Taste the broth, then add a little more fish sauce if it needs saltiness.

If the pepper or shrimp paste tastes particularly strong, 1 teaspoon of palm sugar can round out the broth. Gaeng Liang should not taste noticeably sweet, so use it sparingly.

5. Finish with Hairy Basil

Remove the saucepan from the heat. Add the Hairy Basil leaves and stir just until they wilt and release their aroma. Taste once more, then serve immediately with steamed jasmine rice.

Which vegetables work in Gaeng Liang?

Gaeng Liang is flexible, but the cooking order matters. Add firm vegetables first and delicate ones later so everything finishes at the same time.

Vegetable	What it adds	When to add it
Pumpkin or butternut squash	Soft texture and gentle sweetness	First
Baby corn or sweetcorn	Fresh sweetness and a little bite	After the pumpkin
Angled luffa or courgette	Tender, mild pieces that absorb the broth	During the final few minutes
Oyster or straw mushrooms	Savoury flavour and texture	During the final few minutes
Chayote	Crisp, mild flesh	With the baby corn

Browse our Thai fruit and vegetable selection for fresh herbs, aromatics and seasonal vegetables. The recipe does not need to contain every traditional vegetable at once; a balanced mixture of firm, soft and leafy ingredients is more important.

How to balance the flavour

Gaeng Liang should taste savoury and aromatic, with warming pepper rather than overwhelming chilli heat.

• For more warmth: Pound in a few more peppercorns. This keeps the characteristic peppery flavour.
• For more chilli heat: Add another bird's-eye chilli to the paste.
• If it tastes flat: Add fish sauce a teaspoon at a time. Our guide to what makes Thai fish sauce different explains what to look for when choosing a bottle.
• If it tastes too intense: Add a splash of hot water, then adjust the fish sauce again.
• For the freshest aroma: Add Hairy Basil only after turning off the heat.

Can you make vegetarian Gaeng Liang?

Yes, although it will have a different flavour from the prawn version. Leave out the dried shrimp, shrimp paste, prawns and fish sauce. Use a good vegetable or mushroom stock, add extra mushrooms or firm tofu, and season with a suitable plant-based fermented sauce or paste.

Check every label if you are cooking for someone with an allergy or dietary requirement. Some fermented seasonings contain soya, wheat or other allergens.

Common mistakes to avoid

Cooking every vegetable at the same time

Pumpkin needs longer than mushrooms, courgette and prawns. Staggering the ingredients keeps the squash tender and the softer vegetables intact.

Boiling the prawns for too long

Add them near the end and cook only until done. Overcooked prawns quickly become firm and rubbery.

Adding Hairy Basil too early

Long cooking dulls the herb's bright aroma. Turn off the heat first, then stir in the leaves.

Expecting a coconut curry

The broth should be light. Coconut milk, curry powder and a thick commercial curry paste are not needed for this dish.

What to serve with Gaeng Liang

Serve Gaeng Liang hot with steamed jasmine rice as part of a Thai meal. Its peppery broth pairs especially well with a simple omelette, grilled fish or another mild dish. If you need prawns, browse our frozen seafood range and follow the product's defrosting and cooking instructions.

Frequently asked questions

Is Gaeng Liang a soup or a curry?

The Thai word gaeng covers a wider range of dishes than the English word “curry”. Because Gaeng Liang has a light, clear broth, it is usually described in English as a peppery vegetable soup.

Is Gaeng Liang very spicy?

It does not have to be. Its characteristic warmth comes from peppercorns and fingerroot. The fresh chillies are optional, so you can adjust them to suit your household.

Is Hairy Basil essential?

It is one of the dish's defining ingredients and gives the broth its fresh, lightly lemony finish. Lemon basil is the closest substitute. Thai sweet basil or holy basil will make the soup taste noticeably different.

Can I change the vegetables?

Yes. Keep the total amount roughly similar and choose vegetables with a mixture of textures. Begin with dense vegetables such as pumpkin and add quick-cooking mushrooms and courgette later.

Do I need a mortar and pestle?

It gives the paste a good texture and helps release the aromatics, but a small food processor is a practical alternative. Scrape down the sides as needed and avoid adding too much water.

Can I make the soup without prawns?

Yes. You can leave out the fresh prawns while retaining the dried shrimp and shrimp paste for depth, or follow the fully vegetarian variation above. The result will differ slightly, but the pepper, fingerroot and Hairy Basil should remain at the centre of the flavour.

Find the ingredients for Gaeng Liang

The ingredients that make this soup distinctive are difficult to replace with everyday herbs. Start with fresh Hairy Basil and fresh fingerroot, then choose your vegetables from our fresh produce collection. Muay Supermarket brings together specialist Thai ingredients in one place, helping you cook the dishes you know and discover something new at home.