Preheat your oven to 200°C (390°F) and line a baking sheet with parchment paper to prevent sticking.
Unfold the thawed puff pastry sheets on a lightly floured surface and cut into small squares about 5x5cm. Place these squares evenly spaced on the prepared baking sheet.
Slice the brie cheese into small pieces or thin slices, and place a piece in the center of each pastry square, pressing gently to settle.
Spoon a teaspoon of cranberry sauce on top of the brie in each square, being careful not to overfill to avoid leaks during baking.
Using a pastry brush or the back of a spoon, gently brush the edges of each pastry square with the beaten egg to give a shiny, golden finish once baked.
Arrange the bites in the oven and bake for 12–15 minutes, or until the pastry is puffed, golden around the edges, and the cheese is bubbly and slightly melted.
Once baked, remove from the oven and let them cool for a few minutes—they will be hot and bubbling, so handle with care.
Optionally, garnish with a few fresh cranberries or herbs like thyme or rosemary for added visual appeal and flavor.