Preheat your oven to 180°C (350°F) and lightly grease your mini muffin tin or line it with paper liners for easy removal.
Unroll the puff pastry sheet on a lightly floured surface and use a cookie cutter or glass to cut out small circles about 2 inches in diameter.
Gently press each pastry round into the cups of the muffin tin, forming little cups that will hold the filling.
Bake the pastry shells for about 8 minutes, just until they start to turn golden around the edges.
While the shells bake, combine cranberries with sugar and orange juice in a small bowl, stirring gently until the cranberries are coated.
Remove the pastry shells from the oven and carefully spoon a small amount of the cranberries into each cup, followed by a cube of Brie cheese.
Return the assembled bites to the oven and bake for an additional 10-12 minutes, until the cheese is melted and bubbly, and the pastry is golden and crisp.
Remove the bites from the oven and let them rest for about 5 minutes, allowing the filling to set slightly for easier handling.
If desired, brush the tops with a beaten egg for a shiny finish before baking or just serve as is.
Garnish with chopped fresh herbs like thyme or rosemary if you like, then serve these festive bites warm or at room temperature.