Preheat oven to 400˚F.
In a pot or saucepan, bring 8 cups of water to a boil.
Stir in 2 tablespoons of salt and add the asparagus spears; boil for 2 to 3 minutes.
Drain the asparagus and immediately transfer to ice water to stop the cooking process. Pat dry with paper towels and set aside.
Line a baking sheet with parchment paper and set aside.
Roll out the puff pastry and set on a lightly floured surface. Using a rolling pin, roll it out to a rectangle that’s about ⅛-inch thick.
Transfer the puff pastry to the baking sheet.
Prick the puff pastry all over with a fork.
Bake for 10 minutes.
Remove from oven and transfer the puff pastry to a wire rack to cool down a bit.
Tear the mozzarella cheese into smaller pieces and place all over the puff pastry, leaving about 1-½ inch uncovered border on all sides.
Arrange the asparagus spears on the pastry.
Brush the asparagus with olive oil and season with salt and pepper.
Bake for 15 to 18 minutes, or until cheese is melted and puff pastry is crisp and golden brown.
Remove from oven and drizzle with a bit of balsamic glaze.
Cut into 8 slices. Serve.