Make the buttercream icing by beating together 50g butter and 100 g icing sugar. Add a teaspoon of hot water, beat again, then another 100 g icing sugar, and more water if needed (may need up to 1 tbsp). Taste and check for consistency, and add more butter / sugar / water if needed. Add a little blue food colouring and beat again until the buttercream is uniform in colour. Add a little more colouring if needed to get the shade that you want.
Put the desiccated coconut into a small resealable freezer bag. Add about 1/4 tsp blue food colouring, seal the bag, and squeeze and shake it about to turn the coconut blue.
Put a generous tablespoon of icing onto each cupcake, add more as needed, and shape into a mound. If the cakes are flat, you will need more icing, but if they have risen in a dome shape, you can shape the icing around that.
Tip the coloured coconut into a bowl, and dip in each cupcake, scattering over a little more, and pressing down into the icing, as needed, to completely cover.
Alternatively, if you don't want to use coconut, simply 'fluff up' the icing with a fork or sharp knife to make Cookie Monster's fur. (Both options are shown in the photo).
Leave to set for 10 - 15 minutes.
Warm the bottom of the dark chocolate drops (e.g. with the back of a metal spoon dipped in boiling water) and stick onto the white chocolate buttons. Or, melt a little dark chocolate and spoon or pipe on to make the eyes.
Place the eyes on the cupcakes, in any position that you like.
Cut the chocolate chip cookies in half.
Make a slit for the mouth, squeeze the cake a little, and push in the half cookie. If the cookies crumble, don't worry, as you can put pieces in his mouth instead. Or even break some on purpose to do this!
Smile and enjoy!