Slice the Yellow Onion (1).
Melt the Butter (2 tablespoon) in a sauté pan on medium-low. Add the onions and cook for about 15 minutes until they are caramelized.
Thaw the Puff Pastry (1 box), roll it out, and cut it into 12 equal pieces. Lay each piece over the top of a hole in the muffin tin.
Cut the Brie Cheese (6 ounce) into 12 equal pieces and place one on top of each puff pastry.
Spoon the onions on top of the cheese. Sprinkle each with a small amount of Fresh Thyme (1 tablespoon).
Bake for 10 minutes or until the pastry puffs and the cheese softens.