Preheat oven to 325F/170C. Line 3 cookie sheets with parchment paper or a silicon nonstick baking mat.
In a mixer with a paddle attachment or with a wooden spoon, cream together butter and caster sugar until pale, light and fluffy, Incorporate the egg and vanilla extract and mix until combined.
Mix in the dry ingredients; flour, baking powder and salt until combined. Do not over mix or the cookie will get tough.
At this stage add any additional ingredients such as choc chips, smarties or freeze dried fruit and mix until evenly distributed.
Scoop cookie dough into balls about the size of a walnut.
Place each ball of cookie dough onto the baking sheet lining. Leave an inch or two between each one for spreading and gently flatten slightly.
Bake for about 8 - 10 mins until lightly golden brown.
Cool on a wire rack then enjoy. These keep well in an airtight tin
Recipe by Cluck, Muck & Cook at http://cluckmuckcook.co.uk/traditional-sugar-cookies/