Finely chop the onions and dice the pears. Put the onion in the hot oil and sauté until translucent. Add pear cubes and fry for another 4 minutes. Roll out the puff pastry, cut to size and line the bottoms of the tart forms with it. Fill the tartlets with the onion and pear mixture and cover each with 1 tablespoon of goat cheese. Bake at 190 degrees for 20-30 minutes.