Preheat oven to 425 degres F. Remove the woody ends of the asparagus, although not necessary if using Michigan asparagus. Cut each stalk in half.
Cut puff pastry sheet into 4 squares. Place on baking sheet. Sprinkle 1/4 cup of Swiss cheese on each square. Place 6 pieces of asparagus on each tart.
Bake at 425 degrees F. for 20 - 25 minutes or until golden. Serve immediately.