2 yellow onions
½ cup sugar
2 tablespoons water
½ cup vinegar
1 sheet puff pastry
Preheat oven to 400° F.
Grease six individual ramekins. Slice onions into ½-inch discs.
In a heavy cast iron skillet, carefully brown circles of onion in butter or oil, remove and set aside.
In the same pan, make gastrique by mixing sugar and water and cooking until caramelized, then adding vinegar and cooking down to a syrupy consistency. (You can also use honey and cider vinegar if you prefer.) Pour equal amounts of gastrique into each ramekin and place a circle of onion on top.
Cut out circles of puff pastry to fit into the ramekins. Place one puff pastry circle over each onion circle.
Bake until pastry is golden. Turn out and garnish with whipped goat cheese and herbs. Makes 6 tarts.