Fantastic guide @papa-pepper. I haven't saved mustard seeds yet, simply beacuse I never let it bolt!
There's a lot of good seed saving info on Steemit right now...@project-diaries just did one on strawberries which was very clever. Thanks for the info - I may try my hand at a seed saving for cauliflower post soon!
Even just letting one plant bolt can provide a lot of seed for years to come!