1. Adjust oven rack to upper-middle position and heat broiler. Line broiler-safe baking dish with paper towels. Trim 1½ inches from stem end of asparagus and reserve ends. Bring water to boil in large skillet over medium-high heat. Add asparagus ends and ¼ teaspoon salt and cook, covered, for 5 minutes. Using slotted spoon, remove asparagus ends and discard. Add asparagus stalks to skillet, cover, and cook, stirring occasionally, until nearly tender, 2 to 4 minutes. Transfer asparagus to paper-lined baking dish. Pour asparagus water into liquid measuring cup; reserve 1 cup.

2. Melt butter in now-empty skillet over medium heat. Add flour and cook, stirring constantly until golden, about 1 minute. Whisk in reserved asparagus water and bring to boil. Reduce heat to medium-low and simmer until thickened, 3 to 5 minutes. Off heat, whisk in ½ cup Parmesan and Monterey Jack until smooth. Season with salt and pepper. Cover and let stand for 5 minutes.

3. Remove paper towels from baking dish. Drizzle sauce over center of asparagus and top with remaining Parmesan. Broil until cheese is golden and asparagus is tender, 6 to 8 minutes. Serve

TREASURE NOT TRASH
The asparagus ends make a flavorful stock in which to cook the spears.