Start dark brown thread on a barbless scud hook and tie in seven or eight mallard flank fibres for the tail, then gold wire, then opal tinsel right on top for the flashback.
Dub a body of hare's ear dubbing forward, leaving the front third clear.
Pull the opal tinsel over the body as a flashback. On a small dark nymph the flash strip is the single trigger that makes a fish commit.
Rib the gold wire forward, which both segments the body and pins the flashback down, then tie off and helicopter it out.
Tie in seven or eight pheasant tail fibres for a separate wing case, then dub a thorax of the same hare's ear but a shade darker than the body. A darker thorax reads as the head and legs of a nymph about to emerge.
Add more mallard flank at the front for the legs, pull the wing case over, tie off and trim.
Whip finish and glue the wraps. Fish it slow near the bottom.