1 sheet frozen puff pastry, thawed
1 Tbsp flour, plus more for work surface
Coarse sea salt
1 lb tender asparagus, trimmed, cut into 2-inch pieces, stalks and tips kept separate
2 tsp Extra-Virgin Olive Oil
4 large eggs, room temperature
1 Cup heavy cream
1/2 Cup Gruyere cheese, finely shredded
1/2 Cup fresh goat cheese, roughly crumbled
On a lightly floured work surface, roll out puff pastry into a 14-inch square. Using a sharp knife and an upside-down dinner plate, trace around the baking dish and cut the puff pastry dough into a 13-inch circle. Put pastry dough into a lightly oiled 9-inch round baking dish or a 5-1/2-to-6-cup deep-dish pie plate. Poke dough all over with a fork. Freeze until dough is chilled and firm, about 30 min.
Preheat oven to 350F. Line tart shell with parchment paper and fill it with pie weights or dried beans. Place pie pan on a baking sheet and bake the empty crust until edges turn pale golden brown, about 40 minutes. Remove crust from oven and gently remove the pie weights (or beans) and parchment paper. Return crust to oven and bake until bottom is dry and golden brown, another 5 minutes more. Remove from oven and allow to cool completely on a wire rack.
Meanwhile, bring a medium pot of salted water to a boil over high heat. Add the asparagus stalks and cook until barely tender, about 2 minutes. Transfer asparagus stalks to a bowl of ice water; when cooled, transfer vegetables to a plate and gently pat dry. Now, add the asparagus tips to the boiling water and cook briefly – only 30 seconds should do the trick. Remove the asparagus tips from the boiling water with a slotted spoon or fine mesh sieve, and transfer to the ice water bowl; drain when cool. Pat tips dry (very gently!) and toss with oil in a small bowl.
Transfer asparagus stalks to a blender. Add the eggs, cream, flour, and 1-1/4 teaspoons salt to the blender and puree until mixture is very smooth.
Pour the asparagus-egg-cream-custard into the prepared crust. Sprinkle the eggy batter with the Gruyere and goat cheeses, then top decoratively with asparagus tips. Bake tart until the edges of the custard filling are puffed, the top is golden brown, and center is set (not jiggly), about 40 minutes. (Tent with foil for the last 15-20 min, if necessary, to prevent over-browning.) Remove tart from oven and allow to cool on a wire rack at least 15 minutes before serving.
Make ahead; traveling tart: Crust can be baked empty, then cooled completely, and wrapped in plastic wrap up to 1 day ahead. Tart can be made up to 8 hours ahead and served at room temperature.