Preheat oven to 375F. Line a large sheet pan with parchment paper.
In a large skillet over medium-high heat, add the olive oil.
Add the bacon and leeks to cook until the bacon in almost crispy.
Add the chopped mushrooms to cook another 3-4 minutes, until tender.
Season with salt and black pepper.
Remove the skillet from heat to cool to room temperature.
In the meantime, prepare the puff pastry. On a lightly floured surface, gently roll out the puff pastry so it’s smooth. Slice into 6 equal-sized squares.
On each square, add a spoonful of the mushroom mix followed by a handful of shredded cheddar. Press the opposite edges together to seal the mixture inside the puff pastry. Place on the prepared pan.
Brush with the egg wash, then sprinkle with everything bagel seasoning.
Bake for 30-40 minutes, until golden brown and crispy.
Let cool at least 10 minutes before enjoy warm with Klarbrunn Peach Mango for a complimentary refreshment!