Beat the eggs with the sugar. To them add the flour sifted with the baking powder and vanillas. Pour the mixture into an oven dish laid out with baking paper. Bake the layer at 356°F (180 °C) for 15 min. Take it out and wrap it up using the baking paper.
Boil 2/3 of the milk. In a bowl, beat the eggs with the sugar, vanilla and the rest of the milk. Pour it in a thin trickle into the boiling milk. Stir until thickened.
Pour the cream in a shallow plate and cover with plastic wrap. Leave it to cool, return to the bowl and add 1-2 tbsp of the beaten cream. Unroll the roll, remove the baking paper and smear with the cream.
Sprinkle with the crumbled chocolate crispies (leave a few of the balls for decoration) and put the banana, cut into 2.
Wrap it carefully into a tight roll. Transfer it to a plate and smear with the rest of the cream. Decorate with strips of caramel glaze, cream rosettes and chocolate crispies.