Shortbread Is a traditional Scottish pastry famous for its crumbly sand-like texture and brittle a consistency, this results from the fact that no liquid is used in the recipe. The gluten in the flour 
particles does not create any cohesive structures due to the lack of water, so yielding a crumbly and sandy paste. Shortbread is normally produced by pressing the resulting paste into flat decorative moulds, which are then baked on a tray or non-stick sheet. Traditional Scottish shortbread recipes consist solely of butter, flour and sugar. A typical recipe would consist of 500g of plain flour, 250g of unsalted butter and 125g of sugar, this is often referred to as a 3:2:1 mix. They may vary in the proportion of flour and butter used, some use double the amount of flour to butter by weight, while others will indicate a higher butter quantity so giving a softer texture and more pliable paste. 
The butter should always be at room temperature and cut into small cubes. Always add the sugar to the butter and beat until light and fluffy. Always sieve the flour. Add gradually to the creamed butter and sugar mix, turning lightly. Knead thoroughly. The consistency of the dough is dependent on the amount of humidity in the butter as well as its temperature. If it is too cold or too dry the dough will not hold together for rolling. It could still however be pressed together into a mould. Pastes produced with a higher butter content will need to be chilled before rolling. Some recipes suggest a sprinkle of salt while others stipulate avoiding even salted butter. Salt does far more than simply add flavour when used in foods. As a seasoning, preservative or flavour 
enhancer it begins to affect cakes, pastries, biscuits and breads from the moment it is added. So what exactly does salt do and why would you include it a shortbread recipe? Firstly even a small amount of salt will slow down the chemical reactions that are happening in the shortbread paste, in yeast dough for example the addition of salt slows fermentation activity to a more manageable rate. Salt makes the paste a little stronger and tighter. It improves the shelf life of the finished shortbread, but its effects depend on ambient conditions. Salt is hydroscopic, which means it absorbs moisture. In humid climates salt will trap moisture from the air, so making a crisp crust soggy and shortening shelf life. In dry climates salt helps trap any moisture in the paste for longer, so inhibiting staling and extending shelf life. Salt also adds flavour. It enhances the
natural flavour of other the ingredients including butter and flour. Several verities of salt are available including fine, course, rock salt and sea salt. All types act chemically in the same the same way, with no difference in cooking results. Many variations of the basic shortbread recipe exist. Some include flavourings such as vanilla extract, sour cream almond oil, while others recommend replacing half of the flour with ground rice or semolina. Shortbread should be baked at 350° F/170° C gas mark 6 for 20 minutes 20 until lightly browned. Sprinkle with castor sugar while still warm. Cool on a wire rack and serve as required.