The Kaffir Lime (Citrus x hystrix) also known by the Thai name makrut is one of the glories of the food world. A kaffir lime is roughly the same size as the common lime, but is easily distinguishable by its bumpy surface, like that of a Seville orange, or in some cultivars, a really warty surface. The rind is highly aromatic and is a common flavor component of many curry pastes.
Maybe I'll get into curry pastes in another post (or series of posts: it's a subject that deserves its own book) but here I want to focus on the true gems of this tree, the leaves, which are known as bai makrut in Thai. And it is the distinctive doubled leaves that are used more often than the fruit.
Once you have smelled the addictive floral citrus aroma of kaffir lime leaves, I promise that you'll be hooked. And you'll know immediately that there is no substitute on this earth for these leaves. Trust me, I've tried every substitute under the sun for them and nothing can come close to that haunting citrus perfume.
I hooked several guests at a tasting last evening when I served pan-roasted halibut on a quenelle of beluga lentils with a highly scented broth poured over it. I cooked the lentils in broth infused with kaffir lime, ginger, lemongrass, and garlic; then drained the broth and reduced it again with more of the same aromatics, then a third time with coconut milk. I used the highly reduced coconut milk to bind the belugas into which I mixed more fresh aromatics. Separately, I made a fumet of halibut scraps, shiitake stock, and more of the same aromatics. After infusing the aromatics, I removed them, reduced the fumet to 1/4 volume and clarified it twice. Before pouring it over the fish, I scattered very fine threads of kaffir lime over the soup bowl. When the hot fumet hit the lime threads, the entire dining room was perfumed.
So haunting was the dish that customers wanted to know all about it and we played show-and-tell with the lime leaves in the dining room. Naturally, all the cooks at the table wanted to know where and how to get them.
Fortunately, kaffir limes are being grown in small quantities in the US, so they are readily available on the market, if rather expensive. Wholesale, a pound of leaves—a small mountain—approaches US$50. You can buy them retail in small quantities via Priority Mail from importfood.com. I did a lot of business with them years ago before the restaurant and they are an extremely reliable small family business. Sorry, UK readers (we have a ton of fans in the UK), I have no clue how you go about getting these gems.
A pound of leaves is a lot, enough to jam a gallon-sized freezer bag, and way more than we can possibly use before they go bad. But fear not, they freeze well. Although they lose their bright color in the freezer, the flavor still goes strong up to a year later. And, no need to defrost the leaves to use them; use straight out of the freezer.
A final word about how to use the leaves. I often use them just like bay leaves, to flavor stocks and soups. I mince them and then pound them in the mortar as part of curry pastes, and very frequently, I cut the central rib out of the leaves, stack them, and chiffonade them into very fine threads which I scatter on dishes at the very last moment.