2 Part Technique - Underhook and Head Control versus your half guard can be a worst case scenario in terms of pass defense, but the position is still escapable despite your disadvantages. Utilize the Bridge Escape by using your inside leg to post on the ground for support during the bridge, and use your outside leg to keep him stuck in half guard while you hold his upper body tightly. Sometimes this isn't enough to sweep your opponent, but it does however help create enough space to continue into the Frame Escape. Use the hip escape to recover back into butterfly as you use your forearm to brace against forward pressure from the opponent. If he switches to Over Under Control, again use a combination of hip escapes and framing pressure against his face and head.