Preheat oven to 400 degrees. Place rack in center of oven. Line two baking sheets with parchment paper. Remove puff pastry sheets from freezer and thaw at room temperature for 40 minutes.

While the pastry is thawing fry the bacon until crisp. When the bacon is cool crumble into small pieces.

Next slice and chop the onions. Heat the oil and butter over medium heat in a large saute pan. Add onions, salt, pepper and thyme leaves and saute for about 10 minutes. Reduce the heat to medium low and continue to cook the onions for 15-20 more minutes until the onions are brown and caramelized. Let cool.

The pastry should still be cold, but you will be able to unfold it easily. Flour your work surface and unfold dough. I like to flatten out the dough slightly with a rolling pin. Next, cut each sheet into nine pieces. (see photo) I cut down the fold lines and then I cut each rectangle into 3 equal portions.

With a sharp knife score a small rectangle inside each pastry square to create a little area for the filling to nestle in when the pastry puffs up as it is baked. (Just make a small indent, do not cut all the way through the pastry dough.) Place the squares onto your parchment lined baking sheets about 2 inches apart.

Place some of the shredded gruyere cheese inside the inner scored rectangle. Top with 1 heaping tsp. caramelized onion mixture, a little more of the shredded gruyere and lastly a few pieces of the crumbled bacon. Brush the outsides of the squares with the beaten egg/water mixture. Bake at 400 degrees for 15-17 minutes til puffy and golden brown rotating trays around the 8 minute mark.