Preheat oven to 180°C (160°C fan-forced). Lightly grease a 1½ litre baking dish and place it on a baking tray.
For the salted chocolate caramel sauce, combine the sugar, cream, vanilla and butter together in a small saucepan over medium heat, stirring until sugar dissolves. Bring to the boil and cook for 2 minutes. Remove from heat, allow to cool for 10 minutes. Add chocolate and salt, stirring until melted and smooth.
Meanwhile for the crumble, combine the flour, sugar and cinnamon together in a mixing bowl, stirring to combine. Add the diced butter and using clean fingertips, rub the butter into the flour mixture until the mixture resembles coarse breadcrumbs. Add the coconut, macadamia nuts and chocolate chips rubbing mixture to combine.
Place banana into a prepared baking dish with cornflour, tossing until well coated. Pour over chocolate caramel sauce and sprinkle the crumble on top. Bake in preheated oven for 25 minutes or until crumble is golden and bubbling.
Serve with a dollop of double cream, a scoop of ice cream or custard.