Place the 3 croissants on a baking tray and slice them horizontally nearly all the way through. Put to one side.
In a medium bowl, mix together the ground almonds, butter, sugar, salt, egg and almond extract until combined. Spread all but 2 tablespoons of this mixture inside the three croissants, then spread the remaining mixture on top of the croissants.
Mix the honey and nuts together, and spoon on top of the croissants. Push down a little so they stick to the top.
Place in the oven to cook for 10 minutes (note: this lightly cooks the frangipane, but you’ll need to cook for longer – until the center is piping hot – if you can’t have raw eggs).
Take out of the oven and carefully stuff the centre of the croissants with the banana slices before serving.