I should say that I first had the idea when making a syrup with lemon balm for some jelly. If you've got a garden, this is easy to come by, but if you haven't there is no way you can buy it. I tried, then, substituting lemongrass, weight for weight, and it worked beautifully. By the same token, if you have got verbena in the garden then do use that here.
Photo by Francesca Yorke.
Recipe posted by Nigella