Mustard seed
Mustard seeds are small, about 1mm in diameter. They may be colored from yellowish white to black. They are important spices in many regional cuisines.
In the Indian subcontinent they are often used whole, and are quickly fried in oil until they pop to impart a flavor to the oil.
Mustard oil can be extracted from the seeds. The seeds, particularly the white ones, can also be ground into a flour, and mixed to a thick paste with a little water to make the condiment mustard. The ground mustard powder is usually mixed with ordinary flour to reduce the strength of the resulting condiment.
Other ingredients can be used to mix mustard, for example, sugar, honey, vinegar, wine, or milk.
When initially mixed the sauce is mild in flavor, but it develops in time. Strong mustard has a very powerful (and painful) effect on the nasal membranes if eaten carelessly.
The whole seeds can be soaked in liquid before grinding to create whole grain mustard.
It is possible to buy ready prepared mustard in many places, but the freshly prepared product is usually far superior.