Cream the butter and sugar together using a handheld electric mixer, then sift over the flours. Add the vanilla bean paste, then mix and turn out on to a lightly floured surface. Knead lightly until it comes together, then roll out to roughly ½cm thick.
Using a template made from baking paper, cut out 8cm x 3.5cm bunny mouth shapes. Place on a wide greaseproof paper-lined baking sheet, then stick a wooden skewer underneath and leave in the fridge to firm up for 1 hour. Preheat the oven to 180°C/fan 160°C/gas mark 3.
Once chilled, bake for 15-18 minutes until lightly golden brown. Remove from the oven and leave to cool for 5 minutes, then transfer to a cooling rack and leave to cool completely.
Dust your kitchen side with icing sugar, then knead the ready-to-roll icing until pliable. Roll out until 2mm in thickness and then, using the template for the biscuits, cut out more mouth shapes.
Mix the icing sugar with 1 tbsp cold water. Add a drop more water if it's too thick. Use the icing to stick the rolled-out mouths to the biscuits. Use the black icing to draw a mouth, teeth and whiskers on each biscuit, then add a drop of icing to the back of the Jelly Tots and fix to the centre of each biscuit where the nose would be. Leave to set for 3-4 hours before eating.