Bananas are the fruit of a long-leaved tree, native to India. A single banana tree can bear several clusters, each containing up to 200 bananas.
Whisk egg, egg yolk, corn flour and sugar in a bowl. Heat 300 ml milk in a pan, until nearly boiling. Whisk into the egg mixture.
Return mixture to pan. Stir over a low heat until thickened into a thin custard. Return to bowl. Cover custard with a disc of damp greaseproof paper, to prevent a skin forming. Cool.
Mash the bananas, then fold into the cooled custard with the vanilla essence. Whip the cream into soft peaks, then fold into the mixture. Pour into a rigid plastic container. Cover and freeze for 1-2 hours. Beat well with a wooden spoon to break up any ice crystals, then freeze until solid.
Meanwhile, cut the chocolate bars into pieces and put in the cleaned pan with 4 tabs milk. Stir over a low heat until melted. Serve the ice cream with the warm sauce.
If the custard curdles or separates in step 2, remove pan from heat, add an ice cube to the custard and whisk well. Alternatively, transfer to a blender and blend briefly.
For an extra treat, serve the ice cream and sauce with slices of exotic fruit, such as mango and pineapple.
Look for ripe bananas, avoiding any that have turned completely brown or are very soft or mushy.