On lightly floured surface, gently roll out each pastry sheet to 10-by-12 inches.
Cut each sheet into 30 2-inch squares, ending with a total of 60 squares (a pizza cutter works great for this).
Lightly score each square about 1/8 inch around the edges and prick liberally with a fork. This will keep the pastry from puffing up too much during cooking.
Transfer pastry squares to 2 parchment-lined baking sheets and put into the refrigerator.
Melt butter in large skillet over medium heat.
Add onions to pan and cook for 2 minutes, or until onions are translucent.
Stir in sugar, flour, salt, and pepper and cook, stirring constantly, for 1 minute.
Add sour cream, green beans, and half of cheese to onion mixture and stir until well combined and heated through. Remove from heat and set aside.
Take pastry squares out of refrigerator and top each one with a small spoonful of the green bean mixture and shredded cheese.
Bake in the preheated oven for 7 minutes, remove from the oven. Top each square with a few French fried onions. Return to the oven and continue cooking for an additional 6-8 minutes, until the pastry is puffed and golden. Let sit 5 minutes before serving.