Put the butter and sugar in a medium bowl and beat together until light and creamy. Beat in the egg yolk, vanilla and flour until the mixture forms a dough. Knead until smooth, then wrap in cling film and chill in the fridge for 30 minutes.
Preheat the oven to 180ºC, fan 160ºC, gas 4. Roll the dough out on a lightly floured surface to a thickness of 3mm. Stamp out 10 cookies with the round cutter and put on a non-stick baking tray. Using the mini cutters, stamp out 20 heart and 20 teardrop shapes (you will need to re-roll the trimmings). Put them on another baking tray in pairs so that the straight sides of the teardrop and heart touch - the teardrop forms the bee body and the heart is the wings. Bake the biscuits for 5-8 minutes until golden. Transfer to a wire rack to cool.
Put the icing sugar in a bowl and stir in 3-4 teaspoons cold water until the icing is a thick pouring consistency. Spread the icing onto the round biscuits and the wings of the bees. Then mix in a few drops of yellow food colouring to the remaining icing and ice the bodies of the bees. While the icing is still tacky, decorate the round biscuits using mini jelly beans for petals. When the icing on the bees is dry, use the black writing icing to add stripes, eyes and wing details to the bees.