Preheat the oven to 180°C (160°C for fan assisted ovens)/Gas Mark 4. Line 2 x 12-hole muffin trays with paper cupcake cases.
In a mixing bowl, stir the cake mix, eggs, oil and water gently together, then whisk (by hand or electric mixer) for 2-3 minutes until smooth and creamy. Divide the mixture evenly between the cupcake cases. Bake both trays together in the oven for 18-22 minutes. Remove from the oven and transfer the cupcakes to a wire rack to cool completely.
Spread the cupcakes with the icing, creating a small mound in the middle of each one.
Spray the blades of a pair of kitchen scissors with the cooking oil spray and cut each large marshmallow in half widthways through the thick middle, then cut each half in half again to make 4 lambs ‘ears’ from each marshmallow. Cut all the mini marshmallows in half widthways.
Place 2 chocolate chips, flat side facing upwards, for the eyes and a pink mini chocolate bean for the muzzle on the mound of each iced cupcake. Place 2 marshmallow ears, cut side down, either side of the eyes. Place some mini marshmallow halves, cut side down, all around the ears, eyes and muzzle to resemble wool on each cupcake. Store any leftover cupcakes in an airtight container in the fridge for 2-3 days.