Preheat your oven to 190°C (375°F) and line a baking sheet with parchment paper.
If using puff pastry, roll it out gently on a floured surface to slightly relax the dough, then cut into small rounds with a cookie cutter or glass. Place the pastry rounds into mini muffin tins or on the prepared baking sheet.
In a small mixing bowl, combine the cranberries with sugar, orange juice, and a pinch of cinnamon. Toss gently to coat and let sit for about 10 minutes until the cranberries begin to release their juices and soften slightly.
Drop a small spoonful of the cranberry mixture into each pastry shell, distributing evenly. Follow with a small cube or slice of brie cheese on top of the cranberries.
Bake in the preheated oven for about 15 minutes, or until the pastry edges are golden brown and crispy, and the brie is melted and bubbling.
Remove from the oven and let cool slightly for 3–5 minutes. Garnish with fresh thyme if desired, then serve warm for the best melty cheese and juicy cranberries.