Artemis BJJ (MYGYM Bristol), Can Sönmez, Bristol, UK - 24/02/2017
This is from the same reverse de la Riva position as before, meaning you have a grip on the opposite collar with your shin across, while also hooking inside their leg. You're stuffing their same side wrist underneath your bottom leg. The scenario here is that they are trying to go for an underhook pass on your knee shielding leg. As they bring their arm under, kick your leg up to try and free it, then drive the side of your knee firmly into their shoulder blade. It needs to be the shoulder blade, as too high or too high, they will be able to square back up and recover their poisition.
You're also going to stiff arm with your collar grip, in order to both push their head away from you, while also driving it towards the mat with your shoulder blade pressure. That means you can release your grip on their wrist, instead grabbing gi material by their shoulder (or back, if you have particularly long arms). Shove your forearm into the side of their next, pushing with that as you twist your collar grip for the choke.
Teaching Notes: Testing this out earlier, it definitely need to be a standard fingers in grip for the choke, not thumb in. The main difficulty people had was the placement of their knee on the shoulder blade. In order to get that, you will probably need to shrimp out a bit. Also, I find that it is much easier to do with a bent leg. If the leg is straight it is difficult to get the knee in the right place.