Mix the flour, egg, melted butter, condensed milk and water to form a dough. This can be done by hand or an electric mixer. Knead the dough for 10 minutes.
Cover the dough with a damp towel and leave to rest for 10 minutes, then knead for another 5 minutes.
Roll the dough into a thick rope and cut into 10 pieces.
Roll each piece into a ball using melted butter.
Leave the dough pieces to rest overnight in the fridge.
Oil the work surface with melted butter and start working and stretching the dough, try stretching the dough as thin as possible before it splits using butter to stretch.
Slice the banana and spread across the dough.
Fold the dough into a square, overlapping in the middle and making sure the filling is fully covered by the dough.
Fry in a pan with more butter on medium heat til crisp and brown, flip and brown the other side.
Decorate with Nutella® and fresh fruits.