I make this jam (actually, I suppose it's more like a jelly) every year in early June with big beautiful elderflowers. It requires soaking for 3 days before you can actually make the jam in less than 15 minutes after that. Besides spreading it on bread, you can use it to glaze fruit tarts or as a sweet filling for cakes mixed with cream.
There is no way that a jelly will achieve a set in 5 minutes of boiling even with pectin sugar. I made some yesterday and it was just starting to set at 35-40 minutes. This morning it looks like I have just achieved a set and I'm not going to touch it for 6 weeks or more. It looks good but I should ignore the cooking instructions and start checking for set after 10 minutes on a rolling boil. - 04 Jul 2012
Probably needs a bit longer than 5 mins - 06 Jun 2012
Mine won't set, and there is a lot more of it than 3x500ml jars - 01 Jul 2012