Mount a size 14 1XL dry fly hook and start white 70-denier thread.
Tie in 8-10 white rooster hackle barbs at the bend for the tail, about one body length long, then park the thread about a quarter of the way back from the eye.
Stack a small tuft of white calf tail, cord the thread up with a clockwise spin and tie the tuft in with tight wraps at the 75% point, keeping it from spinning around the shank.
Lift the butts to 30-45 degrees, cut them close and at an angle, then bind them down with loose wraps rearward to make a tapered underbody.
Bring the thread back in front of the wing and take several wraps against the base to prop it upright at 90 degrees, plus a wrap or two around the hair itself to gather it like a parachute post.
Tie in medium silver Mylar tinsel at the front, bind it back to the bend, then park the thread just behind the wing.
Wrap the tinsel forward in touching turns for a solid metallic body, up to the thread, and tie it off with two or three tight wraps; trim the excess.
Tie in a white dry fly hackle with barbs one to one and a half hook gaps long just behind the wing, stem forward, and take the thread to the front.
Wrap the hackle: about four turns behind the wing and three in front, then secure with two or three wraps and trim. The extra wraps are what keep a Mylar-bodied dry floating.
Stroke the fibers back, build a small head, and finish with a four-turn whip finish; trim any stray barbs.