Last Sunday, I was sitting on my usual stool in my usual bar, when my usual bartender asked if he could try an unusual drink out on me (my favourite game). The mystery beverage came with a very green, waxy-looking leaf floating in it. This little leaf was a Makrut lime leaf (often found in grocery stores under the name "kaffir lime leaf"), and the flavour it imparted was mind-blowing. Photo by Claire Lower.
If you've never had the pleasure of tasting this little guy (which is used heavily in Thai cuisine), it's distinct aroma can be kind of hard to describe. It's super fresh, intensely aromatic, and a little citrusy. If I had to pick one word to describe to fragrance, I would go with "beautiful".
To use Makrut lime leaves in cocktails, wack the porous, non-waxy side in your palm a couple of times and just float it in there. You'll be astounded by how much flavour this contributes. Beyond cocktails, these things can be thrown in soups, rice dishes, gravy, pretty much anything. You can find them at Asian grocery stores, and they can be stored in the freezer for months while retaining their flavour.
Ed. Note: Though this leaf may be more popularly known as "kaffir lime leaf", "kaffir" is an ethnic slur targeting Black Africans in South African slang, derived from the Arabic term "kafir", for "disbeliever". While its use in English is purely to describe the leaf mentioned here, we've used the appropriate substitution, "makrut" leaf, instead. For more on this topic, this article from Modern Farmer goes into detail.