Why tonic water in a cold brew drink?
Tonic brings two things that lavender drinks need: bubbles and a touch of bitter snap. Without the tonic, lavender can read flat or perfumey. The carbonation lifts the floral note off the tongue and the quinine bitterness gives the cold brew a counterweight that keeps the whole drink from sliding into dessert territory.
How do you make lavender cold foam at home?
Whisk ½ cup of cold half and half with 1 pump (about 10 ml) of Lavender Coffee Syrup until it thickens and holds soft peaks. A handheld milk frother is easiest. If you're dairy-free, full-fat oat milk works, though it won't get as stiff. The lavender in the foam reinforces the syrup underneath without making the drink twice as sweet.
Can I substitute another syrup for the lavender?
Not really. Lavender is the whole point. Vanilla would dull it, peppermint would clash with the tonic, and mint would fight the floral. If you don't have Lavender Syrup yet, this is the build that gets you to keep a bottle around.
