Slice the onion into very thin rounds using a sharp knife or a mandoline slicer.

Melt eh butter in a nonstick skillet over medium heat.

Once the butter has melted, add the sliced onion. Season with a healthy pinch of salt.

Cook the onion down, using a wooden spoon to move the onion around the skillet as it cooks down to a deep golden brown color. This may take between 25-40 minutes, depending on your stovetop, as well as how comfortable you feel caramelizing an onion. You may lower the heat as the onion continues cooking down if you’re concerned that you might overcook it.

Remove from the skillet and let cool before using.

Preheat the oven to 425°F. Spray a mini muffin tin (preferably nonstick) with nonstick baking spray. Set aside.

Roll the puff pastry into a 10” x 10” square. Slice with a sharp knife or pizza slicer into 24 even slices.

Cut the wheel of brie into 24 bite-sized pieces, too.

Place the pieces puff pastry into the wells of the mini muffin tins, spreading them out.

Sprinkle a few pieces of caramelized onions in the bottom of the puff pastry.

Place the brie slices on top of the caramelized onion.

Add additional carameliezd onion on top of the brie.

Bake in the preheated oven for 17-20 minutes, or until the puff pastry is golden brown and the brie is melted.

Remove from the oven, and let cool for 5-10 minutes.

Sprinkle on the fresh thyme leaves and remove from the pan.

Serve warm and enjoy!