Upside Down Puff Pastry with Balsamic Beets

-1 Preheat the oven to 375 F
-1 Thaw the puff pastry sheet according to the package instructions. I like to roll my pastry sheet out for a thinner crust, or stretch it out with my hands once it's thawed and cut. 
-1 Thinly slice the beet into rounds and then in half using a sharp chef's knife or a mandoline. 
-1 Layer a piece of parchment paper on a large baking sheet. You may need two baking sheets depending on how big they are and how wide your puff pastry is. 
-1 Start layering your ingredients onto the parchment paper by adding a drizzle of olive oil then topping it with a drizzle of balsamic glaze, a few pieces of thyme and salt u0026 pepper. Add 2 pieces of the thinly sliced beets on top of this, then cover it with the puff pastry and press the edges down using your finger or a fork. The pastry should cover all of the fillings, so be sure to stretch it out if needed. *See video above the recipe for guidance 
-1 Repeat with remaining beets and pastry, making sure to separate them enough on the pan so that they don't touch. Once the pastries are all assembled, brush the tops with whisked egg.
-1 Bake for 20-22 minutes, until the tops are golden brown. Remove from the oven and let cool for 5-10 minutes before flipping.
-1 Gently flip each one, then serve with some arugula and feta cheese. For best results, top with the arugula and feta right before serving. If preparing ahead of time, you can keep them upside down so that you can warm them in the oven before serving. 
-1 Leftovers can be refrigerated in an airtight container for up to 4 days, and reheated in the oven or air-fryer