Roll out the puff pastry on a dry surface with the plastic facing down. Place the Brie in the center.
Detach the ends of the dough from the plastic wrap and wrap the Brie making a slight twist at each end.
Brush with egg yolk and bake for 20 minutes.
Heat a skillet to medium temperature. Add the walnuts and chestnuts, also the maple and stir until it boils and caramelizes (about 4 minutes). Serve over cheese accompanied by toast.