Start by using the lid of a small pot to trace circles onto the puff pastry.
Cut along the outline and set aside.
Next, peel the bananas, slice them into thin rounds and set aside.
In a small bowl, add the sugar, the ground cinnamon and mix until well combined.
Next, to assemble, make a cut halfway through the pastry and sprinkle it evenly with the cinnamon and sugar mixture.
Add the banana slices and close the pastry by folding it in the shape of a triangle.
Transfer to a large baking tray and set aside.
In a small bowl, add the egg yolks, the milk and whisk until combined.
Then brush this mixture over the pastries we prepared.
Take to a preheated oven at 180° C (350° F) and bake for 30 minutes.
Serve.