Put the flour and salt into a bowl. Make a well in the middle and pour in the milk and eggs. Whisk until you have a smooth batter.
Add the oil and mix well. Rest for 15 minutes.
While the batter is resting, dry toast the hazelnuts, set aside.
Put the chocolate, broken into pieces, into a thick glass bowl. Put this over a pan of simmering water - making sure the base of the glass doesn’t touch the water. When the chocolate has melted add the vanilla, sugar and half of the cream. Set aside.
Cut the banana into thin slices, then squeeze the lemon juice over them. Set aside.
Dip a piece of kitchen paper in oil. Using this, grease the inside a pancake pan or frying pan. Heat the pan over a medium heat for about one minute.
Add a ladleful of batter to the pan, swirling it round the pan to spread out evenly.
Cook the pancake for about 30–40 seconds, until golden. Using a palette knife, turn the pancake over and cook the other side for 30–40 seconds again. Transfer it to a large plate.
Repeat the above. You should get about 4 pancakes.
Spread some chocolate sauce on half of the pancakes, then add some banana slices and chopped hazelnuts. Fold them in half and half again.
Add the other half of the cream to the chocolate sauce (together with a drop brandy perhaps) and heat it slightly over the pan of water.
Pour this sauce over the pancakes, then scatter some hazelnuts on top and serve immediately.