We used flat silk thread, both in it's pure flat state and also learnt how to twist it (so it looks similar to a superior perlé thread). The shape on the left is done in satin stitch using twisted thread, and the flat silk on the right (the photo doesn't do justice to the amazing sheen). The knots are Japanese knots - similar to French knots, but the technique is slightly different (and, given the state of some of my efforts, much more difficult). The final thing we tried was using fine gold thread. Sewing with the gold was easier than I'd expected, and beautifully rewarding.
One of the lovely things about the workshop was using different tools: an awl, a minimalist pair of scissors and a small, slightly chunky needle with a round, rather than flat, eye (shown next to a size 10 embroidery needle). Apparently the round eye puts less strain on the delicate silk than a flat eye, and the small needle was actually easy to use.
The whole experience was great, an intriguing insight into a different way of stitching led by a real expert.