Chocolate banana sundae
Put the chocolate in a heatproof bowl with the syrup and butter. Heat over a pan of simmering water until melted, stirring until well combined. Remove the bowl from the heat, and stir in the rum.
Whip the cream until just holding its shape. Put a scoop of vanilla ice cream in the bottom of each of four tall sundae glasses. Top with the sliced banana, some chocolate sauce and a sprinkling of nuts.
Repeat the layers, finishing with a generous dollop of cream.