This is one of my favorite poses. It is called eka pada rajakapotasana IV. Eka-one, pada-leg,raja-king kapotasana-pigeon. This is such a very beautiful yet intense pose.
Eka pada rajakapotasana IV is the combination of Hanumanasana (known as the monkey pose or the split) and the eka pada rajakapotasana I.
From Hanumanasana, bend your back knee and grab your back foot until you are stable. Then bend your back so that your back foot (the sole of your back foot) is touching your head.
However,if you still can’t perform the monkey pose, you are welcome to modify. You can place blocks underneath your front thigh to ease the stretch.