Asparagus and Chicken Enchiladas

Bahan-bahan (12 porsi)

• ½ cup (1 stick) butter
• ½ cup all purpose flour
• 3 cups chicken broth
• 8 ounces sour cream
• ½ cup green taco sauce
• Twelve 8 inch flour tortillas
• 3 cups chicken, (cooked and shredded)
• ½ cup sweet onion, (finely chopped)
• 12 ounces Monterey Jack cheese, (shredded)
• 2½ pounds asparagus, (trimmed and blanched)
• ½ cup Parmesan cheese, (grated)