This is a lovely, spicy, warm flavored sauce that can be adapted by adding other ingredients. I often stir in hard-boiled eggs or bread crumbs soaked in vinegar, which adds different textures.
Serve with fish, cooked meats, cheese and salads.
Put the mustard leaves and garlic into a food processor and blend with 2 tsp vinegar. With the processor still running, add the olive oil in a slow stream, season to taste, then add the remaining vinegar if required.
Reprinted with permission from Jekka's Herb Cookbook by Jekka McVicar, Firefly Books 2012.
Darra Goldstein is editor in chief of The Oxford Companion to Sugar and Sweets, an 888-page reference guide to all things sweet. "The book is really a compendium of human desires, a cultural history of desire for things that are sweet and what it has caused in the world, in both the realm of pleasure and also of pain," she says.