What can I use in place of Kaffir lime leaves in making Tom Yum soup?

--Deanna

Finding a substitute has been a bit of a problem for me, too.  Because Kaffir lime leaves, also known as Makrut lime leaves¹, have a distinct floral note just substituting lime zest and/or lime juice has never had the right flavor profile to me.

I did manage to find some dried Kaffir lime leaves, but like so many dried herbs, the bright tastes that come from the more volatile compounds are lost during drying, giving a poor imitation of the taste of fresh leaves.  Then I came across The Food Substitutions Bible by David Joachim.  Joachim suggests, among other ideas, using either lemon thyme or lemon verbena as a substitute.  Neither of those works well alone, but together with lime zest I thought they might come close.

Another suggestion I came across was to use bay leaf along with lime zest.  The idea seemed off the wall to me, but worth a try.

I made tisanes using various combinations of dried Kaffir lime leaves, lime zest, lemon thyme, lemon verbena and dried bay leaf to see if any of them worked.  Here, in the order from those that seemed closest to those that weren't quite as good, are the combinations I came up with.  For each fresh Kaffir lime leaf, use:

• 1/2 of a small bay leaf plus 1/4 tsp of lime zest and 1/8 tsp fresh lemon thyme; or
• 1 dried Kaffir lime leaf plus 1/4 tsp of lime zest and/or 1/4 tsp fresh lemon thyme; or
• 1/2 tsp of lime zest plus 1/4 tsp fresh lemon thyme

To my surprise, a small amount of bay combined with lime zest and lemon thyme worked very well.  You might want to try playing around with the amounts of each of the ingredients to get a taste you like, but these combinations all seemed to be better than just using any one of the substitutes alone.

Lemon verbena can be substituted for lemon thyme in the above blends, but isn't quite as close in taste, to me.  Both lemon thyme and lemon verbena are common garden herbs and can be bought to plant in your herb garden or you may find them at your local farmers' market.

Note that you can use these combinations in dried form and scale them as needed depending on how many Kaffir lime leaves were called for in the recipe.  The tisanes were only to allow for taste testing of the various combinations.

¹Joachim, and others note that the word "Kaffir" has a disparaging connotation and therefore discourage its use, preferring Makrut lime instead. It is also spelled as kieffer or kiefer lime.