Shortbread is a type of biscuit which is traditionally made from one part white sugar, two parts butter, and three parts flour. The use of plain white (wheat) flour is common today, and other ingredients like ground rice or cornflour are sometimes added to alter the texture. Also, modern recipes often deviate from the pure three ingredients by splitting the sugar portion into equal parts granulated sugar and powdered sugar and many further add a portion of salt. Shortbread is so named because of its crumbly texture (from an old meaning of the word short). The cause of this texture is its high fat content, provided by the butter. The short or crumbly texture is a result of the fat inhibiting the formation of long protein (gluten) strands.
Contributions by WhatamIdoing, Derek Ross, and 18.104.22.168.