In a bowl, combine the flour, egg, olive oil, salt, and half the milk. Whisk the batter well, adding the remaining milk, a little at a time, until the batter is silky smooth in consistency.
Heat a hot nonstick skillet. Add a ladle of batter to the hot skillet. Evenly smooth out the batter. Cook until the batter sets and the underside is lightly browned. Run a spatula underneath the crepe and flip over. Cook until the other side is lightly browned. Remove from heat.
Smear the chocolate-hazelnut spread over the crepe and add the bananas to one side. Then fold over the crepe and sprinkle with icing sugar (confectioners'). Serve the crepes immediately.
Repeat the above process with the remaining batter to make the additional servings.