Start by cutting the bottom of the plastic bottles and set aside.
Peel the bananas and place them on an oven rack, with a baking tray underneath for support.
Next, using a rolling pin, press these bananas against the rack, slicing them into rounds.
Then, arrange the plastic bottle bottoms we cut earlier, one next to the other, in rows of 3.
Press the sheet of puff pastry against the bottles, shaping them into little shells.
Now, in each puff pastry shell, add 1 teaspoon of jam.
Add 2 banana slices we cut earlier in each shell.
After that, brush a beaten egg over the entire pastry.
Cover it with another sheet of 300g of puff pastry and using a rolling pin, press the pastry well, trimming the edges.
Remove the excess pastry and unmold all the little shells.
Transfer all of them to a large baking sheet and brush the beaten egg over everything.
Take to a preheated oven at 180° C (350° F) and bake for 30 minutes.
To finish, sprinkle refined sugar to taste over everything.
Serve.