There are three major methods of preparing curries in Thailand. One, more common in the North, is the rudimentary boiling method that involves heating curry paste in water or stock. Fried curries can either involve frying the paste in oil or frying the paste in cracked coconut cream before adding liquid ingredients.
The latter is the least known method outside of South East Asia, mainly due to our lack of hand-making fresh coconut cream, but it’s an important step in most of the typical curries you’re likely to order in a restaurant or prepare at home (e.g. red, green, masuman, panang, etc…).
Cracked coconut cream
When simmered over heat for a short while, much of the water from coconut cream evaporates and then the coconut milk fats and solids separate. When a recipe specifies frying in cracked coconut cream, it’s referring to this separated oil.
If you’ve ever made your own curry paste and added it straight to the coconut milk to simmer then you may have noticed some overpowering flavours dominating, like raw garlic. The reason? The curry paste was meant to be fried first, a process that integrates the flavours. I find this isn’t as great an issue with packaged curry pastes as they’ve had time for the flavours to mellow (think about the difference in garlic pungency between a freshly made batch of hummus versus how it tastes after a day or two).
To make cracked coconut cream, simmer coconut cream over low heat for around ten minutes until the liquid begins to separate into a curdled mass. You will see visible droplets of oil. This is the point at which curry paste is added and fried.
Canned coconut milk and cream is homogenised and often includes stabilisers that emulsify the fat and water in coconut milk, making it often impossible to crack. Brands of coconut milk I have had success with include Arroy-D, Chaokoh, and Kraw Thip (i.e. those without stabilisers and high in fat). Strictly speaking, the coconut cream is the thicker white liquid that rises to the top of coconut milk (this is more apparent if your coconut milk is homemade), but I often tip the whole can in the wok and just wait for the additional water to evaporate out. Same end result.
Nothing can truly replicate curry prepared properly by cracking fresh coconut cream, but not everyone has the time nor desire to go down the road of extracting cream from coconut flesh. My advice in such cases is to try cracking canned milk. If that doesn’t work then an adequate solution is to faux fry curry pastes by adding a little vegetable or coconut oil to the cream/milk.