Many people deride this stroke, but I truly love it. I love it's simplicity, its usability. Its effectiveness. It is the sweep stroke 'strengthened' by the power of leverage.
The setup. From your neutral position with paddle in front of you, slide the paddle all the way to the left. You can go as far as you like, and I like to go pretty far. I don't stop until my right hand is holding the end of the paddle blade. my left hand ends up somewhere near the center of the shaft. Then extend the left side of the paddle as far as you can reach towards your feet, planting it just to the left side of the bow. Your left arm should be straight, with your right hand close to your chest holding the right blade. Then, as always, rotate your torso until the left blade completes an arc and is at the back of the boat. Remember to push with your left foot, just like in the regular sweep, to engage those core muscles. Because you have greatly increased the reach of the paddle by extending you are increasing the amount of leverage that you have. Thereby turning the boat faster. And by adding a little edge control, You can unlock the bow and turn the boat even faster. More on 'unlocking the bow' later.
I love this stroke for when I want to turn 180 degrees quickly. If someone behind you has rolled and is asking for help there is no faster way to turn a long boat around. People don't like this stroke, because they say it takes away your chance to move quickly into your forward stroke. But as you will see in the video, you can quickly move between the two.