Using a 9-inch flat-sided cake pan as a template, cut a circle out from the puff pastry. Using a fork, poke holes all over to provide ventilation. Set aside.
Slice the bananas into rounds.
Preheat oven to 375°F (190°C).
In a large saucepan over medium heat, distribute the water and sugar evenly and cook until light amber in colour, stirring to help melt any lumps, 5-7 minutes. Add the butter, constantly stirring until the colour is a creamy light brown. Add the banana slices, stirring until they are coated in a thick layer of caramel.
Cook for about 15-20 minutes, turning the banana slices constantly so that they bathe in the caramel. Remove from the heat when the caramel has reduced and little remains in the bottom of the pan. Be careful not to burn the caramel, tasting it from time to time to ensure it does not taste bitter.
Arrange the banana slices in concentric circles on the bottom of the cake pan (or a springform pan). Press the bananas tightly against each other, then pour the remaining caramel over the top.
Lay the circle of puff pastry on top, and tuck the puff pastry down the sides of the pan.
Bake for 45-50 minutes until the pastry is golden brown and firm. Cool for about 1 hour, then invert onto a plate.
Slice and serve with vanilla ice cream. Place a gold foil from Easy Leaf Products on the finished tarte.