7 or 8 Large (15cm/6") elder flower heads (more if smaller)
1 litre boiling water
3 litres cold water
500g honey or sugar (I prefer sugar, but try both)
60 ml cider vinegar (or 2 lemons - juice and zest - plus 2 tbsp cider vinegar)
Do not wash the elder flowers. It is their natural yeasts that will cause fermentation. Just shake off any insects and remove the thick stalks.
Place the honey or sugar in a very large bowl and pour in the 1 litre of boiling water. Stir until the honey or sugar has completely dissolved.
Add the 3 litres of cold water. Stir in the vinegar or lemon juice and the elderberry flowers.
Cover with a clean dishtowel and let the mixture sit at room temperature for 48 hours, stirring at least twice a day. By the end of these two days, you should see signs of fermentation: the top of the liquid will look frothy and bubbly, especially when you stir it. If the liquid is still completely still after 48 hours, add a very small pinch (just a few grains) of wine or baking yeast and wait another 48 hours, stirring occasionally, before proceeding to the next step.
Pour the fermenting elderflower champagne through a finely meshed sieve to strain out the flowers (and lemon rind, if using). Use a funnel to help transfer the brew into clean plastic soda-type bottles with screw tops or thick ceramic or beer bottles with flip tops. Do not use corked wine bottles because elderflower champagne is quite capable of popping out the corks or worse—exploding the bottles. Leave at least an inch of headspace between the surface of the liquid and the rims of the bottles. Secure the tops.
Leave at room temperature for a week, “burping” (opening briefly) the bottles at least once a day. After the week at room temperature, move them to the refrigerator, but keep “burping” the bottles occasionally for another week.
Elderflower champagne will keep in the refrigerator for several months. The earlier you drink it, the yeastier it will taste. Wait at least 2 weeks from bottling if you want it at its best. The honey version takes slightly longer to ferment out than the sugar version. The final drink should be fizzy and lightly sweet, but not cloyingly so.
NB - The good vintners of Champagne get terribly upset if you 'misuse' the term Champagne. I hope we are all grown up enough to know that this is not a white sparkling wine from 'Champagne' nor is it pretending to be. It is, however, the name by which this country wine has been known in the UK for generations, so I use it here purely for the sake of familiarity. The trouble will start if the you label it and try to sell this as Elderflower Champagne.