Preheat oven to 400 degrees F (200 degrees C).
Line 14x17 (or thereabouts) baking sheet with parchment paper. Set aside.
Snap or cut the bottom 2 inches off of the Asparagus (1 bunch). Set aside.
Lightly dust a clean surface with All-Purpose Flour (to taste). Unfold the Puff Pastry (1) onto lightly floured surface. Gently roll out the dough until it is just a tad smaller than your baking sheet (about 16x10 if you are measuring).
Transfer puff pastry to parchment lined baking sheet. Using a fork, poke holes into dough at about ½ inch intervals all over the crust.
Lightly brush puff pastry with Egg (1). Sprinkle with Salt and Pepper (to taste).
Evenly spread Gruyère Cheese (2 cup) over puff pastry. Gently press asparagus spears into cheese. Brush with Olive Oil (1 tablespoon) and season with salt and pepper.
Place in preheated oven for 20 to 25 minutes until puff pastry is puffed and golden and the asparagus spears are tender.
Remove from oven and let sit for about 10 minutes before cutting and serving. Can be stored well wrapped in fridge for 3 to 4 days. It is good eaten warm or at room temperature.