A pattern that does an unbelievably good job at getting those large fish resting on the river beds would be the Black Hare's Ear. This variant of the Hare's Ear has been tested first hand for a multitude of specimens and therefore I can personally attest to the lethal nature of the Black Hair's Ear fly.
First cast was victorious! Beautiful 16 incher. Followed by three more. Trout love a black gold ribbed hares ear in the spring!