For best results, bake this in a well-seasoned cast-iron pan. Let it cool slightly before flipping the pan over and easing out the tatin. Serve as a first course or as a main course with salad and cheese for a vegetarian meal. Adrienne made this in a class at Brookside Gardens in May 2016.
2 T butter
1 T olive oil
1.5# boiler onions, peeled and slice in half around the middle
2 T brown sugar
1 T balsamic vinegar
1 C crumbled goat cheese
1 (8 oz.) sheet puff pastry
Preheat oven to 400°. In a 10-inch cast-iron or other oven-proof pan, melt butter with olive oil. Place onion cut-side down in hot fat and cook until onions are soft and turning brown, about 10 minutes. In a small bowl, combine sugar and balsamic, stir to incorporate. Add to onions and let sizzle until they caramelize, about one to two minutes. Remove from heat and let the pan and onions cool about 10 minutes.
Sprinkle 3/4 of the cheese over the onions. Roll out the pastry dough gently and press over the cheese. Prick lightly with a fork. Bake 25 minutes, or until pastry is golden and filling bubbles up around the edge. Set aside for a few minutes, then invert on a plate and sprinkle with the remaining cheese.
Serve warm or at room temperature.