Preheat oven to 400 degrees. While oven heats, place butter in 9-inch pie pan and place in oven to melt. Swirl pan to grease bottom and sides.
Steam asparagus lightly on stovetop or in mircrowave. Place in bottom of pie pan.
Mix milk, flour, eggs and salt in blender until smooth (or whisk smooth in bowl). Pour over asparagus. Bake until puffed and golden brown, 20-25 minutes.
Sprinkle cheese on top, cut into wedges and serve immediately.