Heat oven to 425 degrees. Bake 25-30 min, until pastry is puffed and golden.
In medium bowl, mash together with a fork or wooden spoon the goat cheese, egg, garlic, tarragon, lemon zest, salt and nutmeg until smooth.
With a whisk beat in the creme fraiche until smooth.
On a lightly floured surface, roll out puff pastry into a 13x11 inch rectangle about 1/8 inch thick. Transfer the dough to a parchment-lined baking sheet. With a sharp knife, lightly score a 1/2 inch border around the puff pastry.
Spread the creme fraiche mixture evenly inside the scored border. Line up the asparagus spears on top, and brush them with olive oil. Sprinkle some salt and grated Parmesan over the asparagus.
Bake 25-30 min, until pastry is puffed and golden. Cool for 15 min on baking sheet [or up to 4 hrs before serving]. Sprinkle black pepper, red pepper flakes, shaved Parmesan and tarragon leaves. Drizzle olive oil across the top.
Tip: Except for grated Parmesan and salt, ingredients may be assembled a day in advance. Sprinkle grated Parmesan and salt just before baking.