Preheat your oven to 180°C (350°F). Line a baking sheet with parchment paper for easy cleanup.
Cut the puff pastry sheets into small circles using a cookie cutter or a glass, then gently press each circle into a mini muffin tin cup to form little nests.
Bake the pastry shells for about 8-10 minutes until they turn lightly golden and crisp. Remove from the oven and set aside.
Meanwhile, combine cranberries with orange juice and sugar in a small saucepan. Cook over medium heat, stirring occasionally, until the cranberries burst and the mixture thickens into a glossy sauce, about 5 minutes. Let cool slightly.
Place a small spoonful of the cranberry sauce into each baked pastry shell, spreading it slightly to fill the bottom.
Top each cranberry-filled pastry with a slice or cube of brie cheese, pressing it gently into the cranberry to help it melt during baking.
Return the assembled bites to the oven and bake for another 4-5 minutes until the cheese is bubbly and slightly browned.
Remove from the oven and let cool for 2 minutes. Garnish with a small sprig of thyme if desired, and serve warm for the best melty, flavorful experience.