Beat the cream until almost stiff. Mix in the Nutella.
Cut the bananas into slices approx. 1 cm thick. Place two waffles on a plate. Spread ¼ of the chocolate cream and banana slices on top, repeat the process until all of the waffles have been used. Top with the remaining mixture and banana slices, refrigerate for at least 1 hr.
Melt the cake icing, spread on top of the waffle cake. Decorate with Smarties and hundreds & thousands.