Cooking with Coconut Milk: Thick, Thin and Cracking the Cream

Coconut milk is the ingredient most people associate with Thai curry, and in central and southern Thailand it really is everywhere: in curries and soups, in dipping sauces and desserts, poured over sticky rice and stirred into drinks. It brings richness, a gentle sweetness and a body that softens the sharp edges of chilli and lime.

It is also an ingredient that rewards a little understanding. Thai cooks treat coconut milk not as one liquid but as two, use them at different stages of cooking, and know exactly what they want it to do in the pan.

Hua kati and hang kati

Coconut milk is not the water inside a coconut. It is made by grating the white flesh of a mature coconut, mixing it with warm water, and squeezing hard. The first squeeze gives a thick, rich liquid called hua kati, the head of the coconut milk. Adding more water to the same grated flesh and squeezing again gives a thinner, lighter liquid called hang kati, the tail.

The two have different jobs. Thick milk carries fat and flavour and is used for frying curry paste, for finishing a dish, or for spooning over the top. Thin milk is used for simmering: it cooks meat and vegetables gently and forms most of the liquid in a curry or soup. Many Thai recipes ask for both, and a curry made only with thick milk can be heavy and greasy, while one made only with thin milk lacks depth.

Cracking the cream

The most important technique in coconut curry is what Thai cooks call making the cream break, or crack. Thick coconut milk is heated in a wok or pot, stirring, until it bubbles hard and reduces. After a few minutes the water cooks off and the fat separates from the solids, leaving a pool of clear, fragrant coconut oil with a few curds in it.

The curry paste goes into that oil and is fried, stirred constantly, until it darkens slightly and smells rich and toasted rather than raw. A good sign is when the oil turns red or green with the colour of the chillies and starts to pool around the paste. The process usually takes 5-10 minutes. It cooks out the harshness of raw garlic and shallot and draws flavour from the spices into the fat, which then carries it through the whole curry.

Once the paste is ready, the meat goes in to coat in it, followed by the thin milk or the rest of the coconut milk, and the curry is simmered until cooked. Look for small beads of red oil floating on top of the finished dish. In Thailand that slick of coloured oil is seen as a sign the paste was fried properly, not as a fault.

Fresh, canned or carton

In Thai markets, fresh coconut milk is pressed to order by machine, and many cooks still prefer it. Outside Thailand, most people use cans or cartons, and both can make a very good curry.

• Fresh: the cleanest, sweetest flavour, and it cracks easily. It spoils quickly, so use it the same day or keep it chilled for no more than a day or two.
• Canned: the most useful form for curry. Leave the can unshaken and the thick cream will rise to the top, ready to scoop off for frying the paste. The thinner liquid below works as thin milk. Check the label for a high coconut content.
• Coconut cream: a richer canned product with less water, handy when you want thick milk only.
• Cartons: usually thinner and more uniform, intended for drinking or cooking. Fine for simmering, but harder to crack.

Many canned and carton coconut milks contain emulsifiers and stabilisers, which keep the fat and water mixed. That is convenient in the cupboard but makes the cream reluctant to split in the pan. If it will not crack, simply add a spoonful or two of neutral oil and fry the paste in that. The result is very close.

When to add it

A common pattern for a central Thai coconut curry runs like this:

1. Crack some of the thick milk and fry the paste in it.
2. Add the meat and stir to coat.
3. Pour in the thin milk and simmer until the meat is tender.
4. Add vegetables that need only a short cooking time.
5. Season with fish sauce and palm sugar, then add the remaining thick milk near the end.
6. Finish with herbs such as Thai basil or torn makrut lime leaves.

Coconut milk can split if boiled hard for a long time, and while a little oil on top is welcome, a curry that has separated completely can look grainy. Keeping the heat to a steady simmer after the paste is fried avoids most problems. Some dishes, such as tom kha gai, are never boiled hard at all, which keeps the soup smooth and the galangal fragrant.

Coconut beyond curry

Coconut milk turns up across the Thai table. It is whisked with salt and sugar and poured over mango sticky rice, set into small layered desserts, and stirred into the creamy sauce that accompanies satay. A spoonful of thick cream is often drizzled over a finished bowl of green curry or a steamed fish curry such as hor mok just before serving, both for richness and for looks. In the north, it is the base of the broth for khao soi.

The curries that use none

Not every Thai curry contains coconut milk, and some of the most interesting ones contain none. Coconut palms grow best in the hot, humid lowlands of the centre and south. In the cooler, hilly north and the dry northeast, coconut was traditionally less available, and the cooking developed in other directions.

Jungle curry (gaeng pa) is the best-known example. It is a thin, fierce, water-based curry full of herbs, vegetables and often wild ingredients, and its heat and fragrance hit much harder without coconut to soften them. Northern curries such as gaeng hang lay, a pork curry with Burmese roots, and gaeng khae, a vegetable and herb curry, are also made without coconut milk. In the south, gaeng som and gaeng lueang are sour, turmeric-yellow curries made with water and tamarind.

Cooking a few of these is a good reminder that Thai curry is defined by its paste, not by its liquid. Coconut milk is one way to carry that paste. It is a delicious one, but it is not the only one.