MIx butter on speed 30 seconds/speed 5. Scrape down.
Add sugars and vanilla and mix on 1 min/speed 4.
Scrape down.
Add eggs and mix 2 mins/speed 4.
Scrape down.
Add flours and bi-carb and mix 40 secs/dough setting.
Scrape into a bowl and refrigerate for an hour.
Preheat oven to 180C. Line 3 baking trays with baking paper.
Shape flat dessertspoons full of mixture into balls and place onto baking tray.
Press down gently and press Smarties into each piece.
Bake for 20 minutes, swapping trays in oven if necessary.
Cool on a wire rack