Preheat the oven to 180°C (160°C for fan forced ovens). Line 2 x 12-hole muffin pans with paper cupcake cases.
Open the cake box, remove enclosed frosting sachet and reserve for another use. Make up the cake mix as directed on the box using the eggs, water and oil. Divide the mixture evenly between the cupcake cases. Bake both pans together in the oven for 18-22 minutes. Remove from the oven and carefully transfer the cupcakes to a wire rack to cool completely; about 30 minutes.
To decorate, put 1 1/4 tubs (550g) of the frosting in a large bowl and colour with a little pink food colouring paste or gel to give a pale pink colour. Spread the cupcakes with the pink frosting. Use a teaspoon to top each with a smaller swirl of the remaining uncoloured frosting.
Wipe the blades of a pair of kitchen scissors with a little oil and cut each marshmallow in half widthways through the thick middle, then cut each half in half again to make 4 bunny ear shapes from each marshmallow. Dip the cut sides of each ear into the pink glimmer sugar or sugar crystals to coat.
Arrange 2 marshmallow ears onto the top of each bit of white frosting so they stand upright. Use the mini chocolate beans and chocolate strands to make bunny eyes, a nose and whiskers on each cupcake. Use the black writing icing to dot on the pupils of the eyes. Serve immediately and store any leftover cupcakes in an airtight container in a cool place for 2-3 days.