Sift the flour with the salt into a bowl. Make a well in the center and add the egg and egg yolk. Pour in the milk, slowly, stirring constantly and, when half is added, stir in the melted butter and vanilla. Beat well until smooth. Add the remaining milk, cover and let stand at room temperature for at least 20 minutes before using. The batter should be the consistency of light cream. Heat a well greased 6-inch skillet. Add 1/4 cup batter. Tip skillet from side to side until batter covers bottom. Cook until the bottom is golden brown, turn and remove to a plate. Repeat with remaining batter. Spread a thin layer of chocolate hazelnut spread onto crepe and place banana slices down the center. Roll or fold crepe. Just before serving top with whipped cream.