1 sheet puffed pastry, thawed and rolled out to 12-by-10 inches
1 teaspoon Dijon mustard
20-24 stalks thin asparagus, cleaned and trimmed
½ cup Gruyere cheese, grated
1 egg, beaten
salt and pepper to taste
Preheat the oven to 425°.
Place the puffed pastry on a baking sheet. With a fork, poke surface several times, leaving a half-inch border around the puffed pastry. This docking is to ensure that the dough underneath asparagus stays flat while cooking, and a border of crust forms.
Spread mustard on docked portion of the dough. Lay asparagus in a single layer, widthwise on the dough. Sprinkle with salt and pepper. Brush the beaten egg on the border around the asparagus to make the tart glossy and golden upon baking. Sprinkle with ch
Place in the oven and bake for 18-22 minutes, or until tart is golden brown, and asparagus is cooked. Serve warm, or room temperature.