Spring Vegetable Tart

From the Williams-Sonoma Food Made Fast: Vegetarian cookbook.
Ingredients:
Frozen puff pastry, 1 sheet, thawed
Fontina cheese, 1 cup (4 oz/125 g) shredded
Asparagus, 15-20 thin spears, trimmed
Leek, 1 small, white part only, halved, rinsed, and thinly sliced
Eggs, 2
Milk, 1/4 cup (2 fl oz/60 ml)
Salt
Freshly ground pepper

Preheat the oven to 400 degrees Fahrenheit (200 degrees Celsius). Line a rimmed baking sheet with parchment paper. Lay the puff pastry on the baking sheet. Fold over the sides to make a 1 inch (2.5 cm) rim, overlapping the pastry at the corners and pressing it lightly. Inside the rim, prick the pastry all over with a fork.
Sprinkle half the cheese over the bottom of the pastry inside the rim. Top with the asparagus, laying the spears vertically in a row from one side of the pastry to the other. Sprinkle the leeks over the asparagus. Bake for 15 minutes. Meanwhile, in a bowl, beat the eggs, milk, 1/2 teaspoon salt, and pepper to taste until well combined. Pour the egg mixture over the asparagus and leeks and sprinkle on the remaining cheese. Bake until puffy pastry is puffed and golden brown, about 10 minutes longer. Let the tart stand for 10 minutes. Cut into pieces and serve. Serves 4.