On a lightly floured surface, roll the puff pastry to a larger rectangle, about 10 x 16 inches.
Using a pizza cutter or sharp knife, cut in half lengthwise, then divide each half into thirds, resulting in six equal pieces.
Using a paring knife, score a border around each, about 1/2 inch away from the edges. Dock the inside of the dough with a fork to prevent it from raising too much during baking.
Bake until pale golden, about 12 to 15 minutes.
Remove shells from oven and spread about 2 tsp mustard on each. Sprinkle on cheese, dividing equally between them. Divide the asparagus between the pastries, trying to get an even mix of tops and bottoms on each pastry. Sprinkle on the garlic, drizzle with olive oil, then add salt and pepper.
Bake until the thickest parts of the asparagus spears are tender, 20 to 25 minutes.