Asparagus feuilletes with chive butter sauce

Filling
16 fresh Asparagus tips, about 2 1/2 inches long
3 oz. Brie, cut into 8 slices
1/2 quantity puff pastry
1 egg, beaten
Chive Butter Sauce
2/3 cup unsalted Butter, chilled and cubed
1 teaspoon lemon juice
2 tablespoons chopped fresh chives

1. To make the filling, bring a pan of salted water to a boil, add the Asparagus tips and cook for 2-3 minutes, or until tender. Drain the Asparagus, refresh in iced water for 5 minutes, drain again, then transfer to a plate to cool.
2. Roll out the pastry on a lightly floured surface to a 10 1/2 x 8 1/2-inch rectangle, approximately 1/4-inch thick. Trim the two long sides to straighten them, and cut the pastry into eight 2 3/4-inch diamonds or squares. Place slightly apart on a damp baking sheet and refrigerate for 20 minutes.
3. Preheat the oven to 400 degrees F. Brush the top surface of the pastry with beaten egg. Do not brush the side edges as the egg will set and prevent the pastry from rising. Lightly score the top of the pastry in a crisscross pattern with a thin knife. Bake for approximately 15 minutes, or until well risen, crisp and golden brown. Split in half horizontally with a sharp knife, and scrape out any soft dough. Place a slice of Brie in the pastry cases and top with the asparagus so that the tips are just protruding. Replace the pastry lid and keep warm in a 300 degrees F oven.
4. To make the sauce, bring 1/3 cup water to a boil in a saucepan. Reduce the heat and whisk in the Butter, a few pieces at a time, until the Butter is well incorporated and the sauce is thickened. Season with Salt and Pepper, and stir in the lemon juice and chives.
5. To serve, spoon a little of the chive sauce into each pastry case and drizzle some of the sauce onto the plate. Serve warm.