Preheat oven to puff pastry box temperature, should be 400°F
Roll out your prepared puff pastry onto a gently floured surface and use a rolling pin to thin it out slightly.
Using a 1.5" or 2" biscuit cutter (or a glass with roughly the same diameter) cut out as many circles as you can and set them aside on a parchment paper lined cooking sheet.
Using one size down biscuit cutter, cut out circles from the cheddar slices and place one on top of each puff pastry round. You should have half the rounds topped with cheese. Toss scraps into the broccoli cheddar soup recipe above or save for future cheese shred needs.
Using a pastry brush, brush the edges of the puff pastry round with the egg wash (whisked egg and 1 tbsp water) and then press the un-cheddared round onto a cheddared round. Use a fork to secure the edges together. Lightly brush the top of the poptart with the egg wash and then cut four holes in the top with a knive to let steam escape.
When all rounds are pressed together, top with Tillamook cheese shreds and flaky sea salt. Place in oven for 10-15 minutes until the puff pastry is nice and golden brown.