Step 1

Add butter and olive oil to a large skillet along with the onions and sauté over medium heat making sure to stir every 5 minutes.

Step 2

Cook the onions over medium to medium/low heat, stirring every 5 minutes for 35- 45 minutes. At this point, if the onions become too dry in the pan, add a small amount of chicken or vegetable broth to keep them moist.

Step 3

Continue to sauté the onions for 15 to 30 minutes longer until the color slowly turns from golden brown to a deep amber color. The onions will continue to darken the longer they cook. You will also notice the volume of onions has significantly reduced as well. Once done, season with salt to taste.

Step 4

Transfer the caramelized onions to a bowl and set aside. If making in advance, place the onions in an airtight container and refrigerate until ready to use.

Step 5

Preheat your oven to 350 degrees. Then, remove the phyllo cup shells from the package and place them on a large baking sheet.

Step 6

Fill each phyllo shell cup with about one teaspoon of creamy brie cheese and bake for five minutes.

Step 7

Remove the tartlets from the oven and top with about half a teaspoon of caramelized onions.

Step 8

Garnish the cheese and onion tartlets with fresh thyme. Serve warm or at room temperature.