For the pastry:

1. Using an electric mixer, cream butter and sugar until pale and fluffy. Beat in egg, then fold in flour (I used the lowest setting on the mixer rather than hand-fold it) until just combined (try not to overwork it).
2. Wrap dough in plastic wrap and rest in fridge for at least 20 minutes.
3. Heat oven to 150C (300F). Roll dough thinly (the dough is very sticky, so I found it easier to divide the dough into equal portions and roll them out separately). Lightly grease 8 x 10cm (4 inch) loose-bottomed non-stick tart tins (I used 6 x 12cm (4.7 inch) tarts. Rest for a further 20 minutes then bake pastry cases blind (line with baking paper and fill with baking beans) for 10 minutes or until golden brown. Take out the paper and beans and allow to cool then place the tarts on a baking tray so they can be carried in and out of the oven more easily.

For the caramel:

1. Melt butter and brown sugar in a heavy based saucepan set over a low heat, stirring all the time until the sugar has dissolved.
2. Add condensed milk and bring to rapid boil for about a minute, stirring constantly until mix is a thick, golden caramel. Add salt incrementally and check for taste.
3. Spread caramel in cooled pastry cases to about 1cm (third inch) thickness. Allow to cool.

For the chocolate custard:

1. Turn oven to 100C (212F). Heat cream in a pot until just about to simmer. Take off heat and add chocolate and whisk until completely melted and combined.
2. Whisk in yolks one at a time then mix in the salt. Leave to rest for about 10 minutes to cool, then give it a good stir and pour (it will be quite liquid) over the caramel layer to cover it completely (and take it as close as possible to the top of the pastry case). Any left over custard can be refrigerated and used within 7 days).
3. Cover the tarts with foil and bake for about an hour, or until the filling is just set with a slight wobble in the centre (they will firm up as they cool).
4. Take tarts from oven and allow to cool to room temperature before serving.

To serve:

1. Slice bananas on a slight diagonal and layer gently over top of the cooked custard. Garnish with shaved chocolate and serve with a good dollop of whipped cream. Left-overs can be stored in the fridge.