I love elderflower cordial. I used to settle for commercial versions (some very good). But in June 2014 I walked into a grove of elderbushes in bloom and struck white umbel nirvana. I picked till I was drunk. Then I began to read.
And here is a recipe that made me very happy. The manymany cordial recipes I researched were very similar, though some use even more sugar, and about half called for citric acid. I decided to rely on the acid in the lemons, alone.
Having made many batches over two summers, I know now that fermentation speeds vary. My recipe below calls for 4 days, but recently I made a batch that I bottled only after 8 days, because it started out so slowly (I picked the flowers after rain) and then remained very active. Please do more reading on your own - I am just scraping the top of this fermentation iceberg and rely a lot on instinct.
Elderflower Cordial - a lightly alcoholic fizz
(I use the same method for common milkweed flowers, but with half the lemon juice)
6 oz / or approx. 30 elderflower umbels
1 lb sugar/450 grams sugar
1.5 liters /52 fluid oz/6 cups water
1/2 cup (about 3-4 lemons-worth) fresh lemon juice
Zest of 4 lemons, peeled in strips, without pith
Don't wash the flowers. Instead, shake them upside down over a cloth to evict any small insects. Strip the tiny white flowers from the green stems, using your fingers. Discard as much green as possible (in any plant it will add a tannic note, but with elderflowers the green is toxic). Weigh the flowers, if weighing, and pack them lightly into a large mason jar (I use a 1.5 liter capacity jar). Dump the sugar on top of them, and add the lemon juice.
Add the cool water and the lemon zest and fill the jar to the top (include the zest), stir well, and screw the lid on.
Leave the jar at room temperature for 4 days. While the mixture is sitting out, open the jar's lid once or twice a day to allow any accumulated gas from natural fermentation to escape ("burping"). For the first day or two you may notice no gas accumulation.
Whatever you do, don't just walk away from a sealed jar and forget about it for days or you will have an elderflower detonation on your hands...
After Day 4, strain through a fine mesh strainer or cheesecloth. Bottle, and keep in the fridge.
I found that some live yeast persisted in the elderflower bottles even after 12 months. Basically the cordial is aging on the lees, a Champagne making method. You can disgorge the bottles when all the yeast has settled on the bottom (died). I never have.
To drink, dilute with sparkling water, add to a gin and tonic, or to shaken cocktails (like this one, with vermouth, or this one, with hyssop, or this one, with mint and gin), or simply splash into a glass of prosecco or Champagne.
Good luck not finishing this in a week, flat.
[This was still effervescent one year later.]