Preheat the oven to 180℃/ 350℉/ Gas 4. Prepare a few large baking sheets/ trays, and line them with greaseproof paper or baking paper.
Place the butter and soft light brown sugar in a mixing bowl. Using a handheld mixer, whisk them until you get a creamy buttercream in a pale colour.
Sieve the plain flour and baking powder.
Fold the flour mixture into the butter mix. Use a spoon or your hand to mix and knead a little until you get smooth cookie dough.
Add the smarties into the dough and leave some for decoration. Quickly mix the dough and smarties.
Bake the smarties cookies in the preheated oven for 10-15 minutes until lightly golden.
Leave the cookies to cool on the baking sheets for 2-3 minutes before transferring them to a cooling rack.
Notes
If you don’t have plain flour, you can use self-raising flour. Just make sure you omit the baking powder if you choose to do so.
Bake longer (15 minutes or more) if you prefer crumbly cookies. And bake them shorter (about 10-12 minutes) if you like soft and slightly chewy cookies.
Nutritional info in this recipe is only estimate using online calculator. You should refer to it as a guide only. Please verify with your own data if you seek an accurate info.