In a medium sized bowl, mix together the condensed milk, butter and brown sugar until combined.
Heat in the microwave for 30 second increments until thick. Stir after each interval.
Peel and core the apples. Cut them into 1cm cubes and place them into a medium sized bowl.
Add the brown sugar, cinnamon and water and stir.
Heat in the microwave for 4-5 minutes, stirring after every 1 minute interval, until soft.
Drain the excess water out of the bowl and set aside.
Cover a flat baking tray with grease proof paper and place the puff pastry sheet in the centre.
Using a knife or pizza cutter, slice the sides of the puff pastry into 4 cm strips. Make sure you leave enough space in the middle for the caramel and apples.
Make two cuts in the middle at the top and bottom of the sheet to fold over and encase the filling.
Spread 3-4 tablespoons of the caramel over the middle of the sheet.
Top with the apple cubes.
Fold over the top and bottom pieces of pastry and begin to braid. This is done by taking one left strip and crossing it over the filling until it reaches the other side and then taking one right strip and crossing it over the filling until it reaches the other side.
Repeat until the braid is finished.
Brush the pastry with the egg white and bake in the oven for approximately 15-20 minutes, or until golden brown.
Serve hot or cold by itself or plated up with whipped cream, fresh berries and melted chocolate.