A brunoise is a particular type of cut used in the culinary world and is specifically a French culinary term that has extended beyond French cuisine and into worldwide usage. In general, it can often be used to refer to a food, often a vegetable such as a potato, which has been diced. Specifically, a brunoise is a dice of 1/8 inch (3.175 mm) cube size, with other sizes of diced product having other names. These names include a dice, a fine dice, and a fine brunoise.
The first step toward cutting a brunoise dice is typically to create long thing sticks through a process generally referred to as a julienne, allumette, or batonnet, depending on the size of the sticks. This is often done with fairly firm products such as potatoes, and begins with squaring off the sides and each end of the item until it has six flat sides like a rectangular box. The squaring off is done to give stability to the item being cut and to make the final product easier to create.
Depending on the size of the cubes desired — and for a traditional brunoise dice they should be 1/8 inch (3.175 mm) — the item is then cut into long slabs of the proper width. These slabs are then stacked on top of each other, only about three or four high to avoid slipping while cutting, and then cut into long sticks of 1/8 inch (3.175 mm) wide. This process of creating these sticks is referred to as an allumette cut, while batonnet refers to sticks of 1/4 inch (6.35 mm) width and height, and julienne typically indicates 1/16 inch (1.5875 mm) size sticks.
The sticks are left together in stacks, and the knife is then brought along them going perpendicular to the cuts that have already been made. This is the brunoise cut that creates the cubes of 1/8 inch (3.175 mm) on each side. Quick, precise cuts can be made down the stacked sticks to create small cubes of the appropriate size for any of the other cuts as well.
General terms used for these types of diced foods typically include a large dice that produces 3/4 inch (1.905 cm) cubes, a medium dice of 1/2 inch (1.27 cm) cubes, and the small dice of 1/4 inch (6.35 mm) cubes made after sticks prepared through batonnet cutting. The 1/16 inch (1.5875 mm) cubes made from julienne cut items are typically referred to as fine brunoise. These cubed foods can be used for a number of different applications, and the uniform size of them is important in cooking to ensure each piece cooks at the same rate.