Mustard is a familiar flavour enhancer and is made in different ways in different countries. The basic ingredients in each country are the same: vinegar, mustard seeds, water, and salt. Mustard seeds are also used whole, for instance in Indian cuisine. Grinding mustard seeds releases molecules that make mustard spicy. If you don't grind the mustard seeds but instead toast or bake them, no spicy substances are released and the taste becomes nutty and bitter.
Basic techniques: pickling, confiting, caramelising, finely grinding.
Taste combinations: cucumber, apple, avocado, beetroot, cabbage, cheese, chicken, coriander, crab, sour cream, cumin, curry, dill, egg, fennel, fish, garlic, broad beans, honey, lamb, onion, parsley, pork, potato, salmon, soya sauce, sumac, tomato, walnuts.