Food is cooked covered in boiling (100°C) liquid, such as water, stock or milk. The surface of the liquid bubbles. This stirs the mixture.
Simmering is when the liquid is brought to the boil, then the heat is reduced enough to keep the temperature just below boiling – about 98°C.
Food is cooked in liquid, such as water, stock, or milk, heated to a temperature between 93°C and 98°C (below boiling point). The surface of the liquid barely trembles. Food may be completely or partially covered by the liquid.
Small pieces of food are cooked slowly in a small amount of simmering water, stock or sauce in a container with a lid. The container may be heated in an oven at a temperature of 160°C or on a stove top.
Food is cooked slowly in an oven in a covered pot or dish. It is partly covered with liquid, such as stock.
Food is cooked in steam (water vapour). It is not immersed or covered in water.
Sous-vide cookery is also called vacuum pack cookery. Raw food with seasoning and cooking liquid is cooked inside a vacuum-sealed plastic pouch in a steamer at a precise temperature. When cooked, the pouch is quickly cooled and held at a temperature of 3°C until needed for service. The food is reheated in the pouch by boiling or steaming.