Preheat oven to 170 C / Gas 3. Using butter or a small amount of cooking oil, grease your trays and set them aside ready for later.
Sift together the flour, salt, and baking powder or bicarbonate of soda into a bowl, and then put this to the side for now.
In another bowl, cream together your softened butter, brown sugar and also the caster sugar, until it is soft, light and fluffy. Spoon in the vanilla extract and mix.
Crack one egg into a cup or small bowl and beat with a fork. Add this gradually, stirring after each splash. Then add the yolk from the other egg and mix well until light and creamy.
Empty your Smarties® into the mixture and mix with a wooden spoon after each tube has been added. This step can be varied by preference, but if you want plenty of Smarties® goodness in there, I suggest using all 5 tubes!
Using your fingers (or a tablespoon if you wish) grab golf ball sized amounts of the mixture, making sure there is an even amount of Smarties® in each blob, and put them onto the greased tray. Pat them down a little but DON'T flatten them. Space them out evenly too, I'd say about 5cm apart, to avoid them sticking together if they decide to spread too far!
Bake in the centre of the oven for 15 minutes. Check them after this time, and if you think they could do with a little longer, leave them for about another 2 minutes but be sure to keep an eye on them.
Once removed from the oven, let them cool a little, and then using a fish slice carefully transfer them to a wire cooling rack to cool completely.
Et Voila! Perfect Smarties® cookies to share with all your friends (if you can resist eating them all yourself!) :)
Soften the butter by microwaving it for around 30 seconds to a minute, depending on wattage variations.
Separate the yolk from the egg white by cracking the egg in half over a cup/bowl and tipping the yolk between each side of the shell, letting the white fall into the container below but keeping the yolk in the shell.
There seems to be an important step missing, the dry ingredients were put to one side but were never mixed with the wet ingredients. I hope I mixed them at the right point. They are in the oven now so we'll see how they turn out - 15 Jun 2014