Slide a gold tungsten bead onto the caddis hook, push it to the eye, and start the yellow Perdigon body thread behind it.
Wind the flat thread back to the bend and forward again in touching turns to build a smooth, lightly tapered underbody. Flat thread lies down without lumps, which matters because the yarn sits directly on top of it.
Tie in caddis-green Mojo Yarn at the bend and wind it forward to about the 70% mark. The yarn gives the mottled, slightly translucent green of a real grannom larva and it is almost indestructible.
Tie off the yarn, then tie in two or three peacock herls behind the bead and wind a short, dense thorax hard against the bead.
Secure the herl with a couple of tight turns and whip finish. Peacock iridescence against a green body is the classic caddis-nymph signal and needs no extra flash.
Fish it as the point fly through spring riffles, especially in April when grannom are abundant and trout and grayling are locked onto small caddis nymphs.