Effortlessly impress your guests with this rich, savory, and flaky appetizer.
Lightly flour a work surface and roll out the puff pastry into an 11×14-inch rectangle. Transfer the pastry to the prepared baking sheet.
Using a fork, prick the pastry all over to keep it flat. Brush the surface evenly with Dijon mustard, leaving a 1-inch border around the edges.
Sprinkle the minced garlic, minced shallot, and shredded Gruyère cheese inside the border, then arrange the asparagus spears neatly on top.