Set your oven to 375°F (190°C) and coat a mini muffin pan with a light layer of grease.
Unfold the puff pastry sheets, slice them into 24 equal squares, and fit each square into a muffin cup.
Cut the brie into 24 small cubes, then drop one cube into each pastry-lined cup.
Add roughly 1 teaspoon of cranberry sauce on top of the brie in each cup.
Beat the egg in a small bowl, then use a pastry brush to apply it to the exposed pastry edges.
Bake for 15–18 minutes or until the pastry turns golden brown. Let them rest for 5 minutes before removing from the pan.