Cream the butter and sugar with an electric mixer until pale and light.
Add vanilla essence and mix well. Add the egg and mix thoroughly.
Sift together the flour, baking powder, Bi-Carb and salt. Gradually add to the creamed mixture to form a dough. Wrap dough in cling film and refrigerate for an hour.
Preheat oven to 170C. Line three oven trays with baking paper.
Lightly flour the work surface and roll out the dough evenly to a thickness of approximately 5mm. Using bunny cookie cutters, cut out shapes from the dough and arrange on the prepared baking tray.
Bake for 10-12 minutes on the middle shelf. Allow the biscuits to cool completely before decorating.
To decorate, roll out the fondant to a 2mm thickness (dusting the surface with cornflour). Using the same cookie cutter, cut out bunny shapes. Brush the cooled biscuit with a small amount of water and stick the fondant to the biscuit, aligning the shapes as best you can. For the tail, dollop the melted chocolate and sprinkle generously with 100s and 1000s.