This step can be done ahead and refrigerated or frozen until needed. If freezing make sure to thaw the onions before assembling the tartlets.
Add olive oil and butter to a large skillet over medium-low heat. Add onions to the pan and gently cook for 20 minutes. Do not let them brown. Keep them over a low heat if the are cooking to fast and stir occasionally. Add garlic and cook for 1 minute. Add salt, pepper, sugar and thyme and cook for 2 minutes. Add white wine and cook until the liquid evaporates. The onions should be beautifully brown and sweet.
To make the tartlets
Preheat oven to 400 degrees.
Open thawed puff pastry onto a floured surface. Cut tartlets into 2-3 inch circles or squares. Use scraps for another use. Put the tartlets on two parchment covered baking sheets.
Score a 1/4 inch border around the tartlets with a sharp knife (but don't cut through the puff pastry) and prick the center with a fork.
To assemble tartlets
Sprinkle Parmesan cheese on the puff pastry inside the scored line. Add the caramelized onions next. Then add a crumble of JOAN OF ARC Garlic and Herb Goat Cheese and put 3 small slices of tomatoes on top of that! Finish with a sprig of thyme.
At this point the tartlets can be covered and refrigerated for up to a day before baking.
Bake at 400 degrees, uncovered, for 20 -25 minutes until puffed and melty and golden!
Serve immediately!