Elderflower and rhubarb jam

pickleandpreserve.co.uk. Makes 2kg. 10 steps

6 large heads elderflower	tie in muslin bag	Mix together in non-metallic bowl, cover. Leave 24 hours, stirring half way through.	Heat slowly without boiling until all sugar has dissolved and rhubarb is pulpy.	Leave in non-metallic bowl, covered, 12 hours.	discard elderflower
1.5kg rhubarb	cut into 2cm lengths				keep rhubarb	Combine, bring slowly to a boil, boil rapidly until setting point is reached.	Pot in sterilised jars while still hot.
1.5kg sugar
1 lemon's juice

According to another recipe, the second "leave in a bowl" is unnecessary.

According to downsizer.net, you can add elderflower to any jam recipe you like. Rub the flowers from the stalks, place the flowers in a jelly bag, and cook with the jam.