Traditional Scottish Shortbread

Preheat the oven to 160?C or Gas Mark 3 Sift the plain flour, ground rice and salt into a bowl. Cut the butter into little cubes and add them to the flour. Tip in the caster sugar. Using your fingertips, rub the butter into the flour, just as if you were making pastry. When the butter has been absorbed, you'll be left with a sandy sort of mixture. Start to clump it together with your hands until you get a smooth, cake-like mass. The butter will hold everything together so no need to add any other liquids. Put the mixture into the centre of a cake tin about 20cm in diameter which has been greased. Using your knuckles or the back of a spoon, gently press out the shortbread to fit the tin in an even layer. Score in lines where you will cut later. Also using a fork, gentle pierce the top of the shortbread all over, try to make it decorative. It should divide into about 16 pieces. Put the tin in the oven and bake for about 15-20mins, until the shortbread is just beginning to take on the faintest trace of colour. This cooking time may vary, I have sometimes found it can take up to 45 mins to cook throughly. Remove from the over and place on a wire rack in its tin to cool.