Prepare the sweet pastry by rubbing the cold butter with the flour and icing sugar until a fine crumb is achieved. Add the egg yolks and bring together. Wrap in cling film and chill for at least two hours.
Place the tins of condensed milk into a heavy bottomed pot and cover with water and simmer for three hours. Keep covered with water at all times, remove after three hours and allow to cool completely.
Roll out the pastry and line individual pastry rings leaving the pastry over hanging until the baking is complete. Blind bake until the base is golden brown. Allow to cool, and then trim the edges. Melt chocolate then line the inside of the pastry case with a thin layer of chocolate.
Combine the crème friache and the mascarpone in a bowl. Then fold through the caramelized condensed milk to create a ripple effect. Deposit it evenly between the tart bases.
Slice the bananas and gently pan fry in a little butter until golden. Arrange them on top of each tart and drizzle with warm chocolate sauce.
Please take extreme caution when boiling the tin of condensed milk as it can be dangerous. You can purchase pre-made caramel as an alternative.