In a deep heavy based frying pan (20cm diameter and oven proof) melt the butter with the sugar. Cook over a low heat for approx. 2 minutes until it turns into a golden caramel.
Place some of the fruit around the outside of the pan creating a circle and then place the remaining fruit in the centre breaking accordingly making sure all the base is covered and cook for approx. 3 minutes. Sprinkle over the chocolate chips and crushed nuts.
In the meantime unroll the puff pastry onto a floured surface and cut a disc shape approx. 25cm. Lay the pastry on top of the fruit and using your fingers push the edges down the side of the pan. Bake the flan in a pre-heated oven of 200º for approx. 20-25 minutes or until the pastry is golden brown. Once ready allow to cool for approx. 5 minutes. Take a large serving plate and place face down on top of the pan turning the tart upside down gently. Remove the pan leaving the fruit flan facing upwards. Slice a generous portion on a plate and serve with ice-cream.