A quick app!

1 large egg
1 tablespoon water
1 lemon (zested)
3/4 cup Parmigiano-Reggiano (finely grated)
5 sprigs fresh thyme (leaves only)
1 package puff pastry (thawed, 2 sheets)
1/4 cup flour (for dusting)
1 cup Gruyere (finely grated, divided)
30 spears asparagus (ends trimmed, cut into 2-inch pieces on a bias)
Flaky sea salt (to taste)
Coarsely ground black pepper (to taste)
1/4 cup dry white wine
3 tablespoons white wine vinegar
2 teaspoons Dijon mustard
1/2 shallot (peeled, finely minced)
1 stick unsalted butter (chilled, cut into cubes)
Kosher salt and freshly ground black pepper (to taste)
Preheat oven to 400ยบ F. Line two baking sheets with parchment paper. Set aside.
In a small bowl, add egg and water and whisk to combine. Set aside.
In another bowl add lemon zest, Parmigiano and thyme. Stir to combine and set aside.
On a floured surface, working with one sheet at a time, unfold puff pastry. Using a floured rolling pin, gently roll pastry into a 10 x 15-inch rectangle. Using a sharp knife, cut into five,15 x 2-inch strips. Then cut strips into thirds, resulting in fifteen, 2 x 2-inch squares. Repeat with second sheet of puff pastry.
Sprinkle each strip of puff pastry with 1 tablespoon of Gruyere and place asparagus in center of strip. Wrap strip around asparagus, taking care to leave no gaps. Gently press edges of dough to seal together. Place seam side down onto prepared baking sheet. Repeat with remaining asparagus, leaving a 2-inch space between each wrapped asparagus. Brush tops with egg wash, sprinkle with lemon zest mixture and season with flaky sea salt and pepper to taste.
Place into oven and bake until golden brown about 15-18 minutes. Transfer to platter and serve with Dijon Buerre-Blanc.
For the Dijon Beurre-Blanc sauce: In a medium sauce pan, add wine, white wine vinegar, Dijon mustard and shallots. Stir to combine and bring to a boil. Lower heat to a simmer and reduce by half, about 2 minutes. Further reduce heat to low and then add butter by continuously whisking the liquid and adding one cube at a time. Wait to add the next cube until the previous one added has fully melted.
Remove from heat and season to taste. Serve along side asparagus.
Tip: Make ahead of time and freeze for the perfect appetizer for that last minute holiday party!