These cupcakes are best made the day before. To make caramel; put sugar and water in a large saucepan over a medium heat and stir until sugar dissolves. Bring to the boil and without stirring, boil for 10-12 minutes until mixture begins to turn amber. Swirl pan to distribute colour evenly.
Remove from the heat and add butter, stirring with a wooden spoon until combined. Mixture will splatter and foam. Pour in cream and whisk until smooth. Set aside until cooled completely. Caramel will thicken as it cools (store at room temperature for a spreadable consistency).
Preheat oven to 200°C. Line 14 holes of two standard-size muffin tins with paper cases. Sift flour into a bowl and stir in sugar. In a separate bowl, whisk together milk, oil, mashed banana and eggs.
Stir wet ingredients into dry ingredients until combined. Spoon into paper cases until three-quarters full. Bake for 20-25 minutes or until a skewer comes out clean when inserted into cakes. Leave in tins for 10 minutes before turning out onto a wire rack to cool.
Just before serving, make creamy frosting; put the marscapone, cream and icing sugar in the small bowl of an electric mixer and beat until firm peaks form and mixture is thick enough to pipe. Fill a large piping bag fitted with a 1cm star pipe with creamy frosting.
Trim tops of cakes to make a flat surface. Spread a spoonful of caramel on top of each cake in the centre, then pipe frosting on top. Keep cakes in fridge until ready to serve and decorate.
Top with a slice of banana and drizzle with golden syrup just before serving.
Tip: Store leftover caramel in a jar in the fridge. Warm caramel to soften after refrigeration.