Preheat the oven to 425℉. Spray two 9x9 inch glass dishes (or one large 9x13 inch glass dish) with nonstick spray.
In a medium saucepan, melt the butter over medium heat. Whisk in the flour and cook, stirring 1 minute. Gradually add the broth and cook, whisking, until thick (about 5 minutes). Remove from heat. Whisk in the sour cream and taco sauce and set aside.
Lay out a tortilla onto a working surface. Place 2 tablespoons of Jack cheese, ¼ cup chicken, onions and asparagus down the center of the tortilla. Spoon 3 tablespoons of the sauce on top of the mixture. Roll and place seam down. Place 6 enchiladas in each dish. Sprinkle with Jack cheese, sauce and Parmesan.
Bake for 25 minutes, or until light golden color and bubbly.
Notes
If you like spicy, add red pepper flakes or a couple of dashes of tabasco to the sauce.
Don't pre-cook your asparagus too long. They should still be firm and crisp.