Grease a 24-cup mini muffin pan (or 2, 12-cup mini muffin pans).
Unfold thawed puff pastry sheet on a lightly floured surface. Roll pastry into an even 10 x 15-inch rectangle. With a sharp knife or pizza wheel, cut into 24, 2 1/2-inch squares (Rectangle should be 4 squares wide and 6 squares long).
Press pastry squares into greased mini muffin tin so that the squares form even cups for filling. Bake 10 minutes.
Remove partially baked pastry from oven and press center of each pastry cup down gently with the handle end of a wooden spoon. Place once cube of brie and a teaspoon of cherry preserves into each cup. Return to oven and bake 10 minutes more. Remove from oven and allow to cool slightly. Sprinkle chopped walnuts evenly over cups and top each with several thyme leaves. Transfer bites to platter and serve.
Video
Notes
Freeze brie for 15-20 minutes for easier slicing. Take care not to overfill pastry cups or cheese will bubble over.
Buy pre-toasted nuts or buy raw nuts and toast them yourself. Toast raw walnuts on a parchment lined baking sheet in an oven preheated to 350˚F for 7-10 minutes, checking often. Toast raw pecans the same way, but you may need to reduce the baking time: 6-8 minutes.
Recipe can be easily doubled to make 48 bites for larger gatherings.
To make up to 3 months ahead, bake bites as directed. Once cool, freeze in a single layer on a baking sheet. Transfer to freezer safe container, separating layers with wax or parchment paper. Reheat from frozen on a parchment lined baking sheet in an oven preheated to 400˚F for 4 to 5 minutes until hot.