Two years ago I made Elderflower wine. I can’t say it was a complete success. Making elderflower cordial, however, always succeeds! There are many recipes online — the ingredients are approximately:
30 flower heads – flowers removed
2 liters of boiled water, cooled
1 kg sugar, honey, agave, etc.
I like to add ginger and mint, too.
Some people like to put everything in one pot. Some people like to steep the flowers and then add the rest. Others like to make a syrup and then add it to the flowers. I have made it all the different ways & find they all work just swell.