A small mill, electric or hand-cranked, that reduces whole spices such as cumin, coriander, peppercorns, cardamom and dried chillies to powder just before they are used. Whole spices keep their volatile oils for years; ground, they fade in months, so grinding fresh is the single biggest step up in flavour for curries, rubs and spice blends. Electric blade grinders, often sold as coffee grinders, do it in seconds; a mortar and pestle gives more control over coarseness and is the traditional tool.
Toast the spices in a dry pan first to deepen the flavour and dry them for a finer grind. A grinder kept for spices alone avoids tainting coffee; grinding a spoonful of rice cleans out the last blend.