Witch’s Brew
The Witch’s Brew is a colour-changing gin serve built for the one night of the year when theatre outranks subtlety. Stirred with butterfly pea flower syrup, the gin pours a deep, inky blue and sits in the coupe looking entirely too calm. The second act arrives at the table: a small jug of lemon juice and elderflower liqueur, poured in front of the drinker, moves the drink from blue to violet in seconds. The trick is chemistry rather than sleight of hand. Butterfly pea flowers carry anthocyanin pigments that read blue in a neutral spirit. Lemon juice lowers the pH, the pigment molecules change form, and the colour shifts through purple towards pink. Nothing artificial, nothing hidden, just an acid doing what acids do. Underneath the performance sits a proper drink. Gin carries the botanicals, elderflower liqueur rounds the citrus, and the pea flower syrup brings sweetness with almost no flavour of its own, which is exactly the point. Halloween claims it first, but it works on any evening that has reached the hour for a small piece of magic.
Glassware: Coupe Glass
Garnish: None: the colour change is the theatre
Ingredients
45ml
A classic London dry. The botanicals stay legible under the colour, and the juniper gives the elderflower and lemon something to push against.
20ml
Colour and sweetness in one measure, blue at rest and violet once the acid arrives. It contributes almost no flavour of its own, which is precisely what the recipe wants.
20ml
Half of the second stage, poured at the table. It is the acid that turns the colour, and squeezing it fresh matters as much here as in any sour.
15ml
The other half of the table pour. Floral weight that rounds the sharpened citrus and keeps the drink from reading as lemonade once the lemon lands.
Instructions
Stir the gin and butterfly pea flower syrup with ice until well chilled.
Strain into a chilled coupe. The drink will sit a deep blue.
Combine the lemon juice and elderflower liqueur in a small jug.
Pour the citrus mix into the drink at the table and watch the colour shift from blue to violet as the acid reaches the pigment. Stir once to settle.
Expert Tip
Make the citrus jug up in advance and keep it cold. The colour change is sharpest when both stages are properly chilled, and a warm pour muddies the violet into something closer to grey. Chill the coupes too, and pour the citrus slowly over the surface rather than tipping it in. Poured slowly, the colour sinks through the glass in a visible band and takes several seconds to complete. Tipped in, it happens all at once and the best part is over before anyone has looked up. One stir to settle. The blue stage is stirred rather than shaken because there is no juice or egg in it to need aeration, and a clear, still glass shows the change better than a cloudy one. If you are batching, stir the blue stage ahead and hold it in the fridge, but keep the lemon out until the glass is in front of someone.
Flavour Profile
The Chemistry
Colour-changing drinks usually earn their reputation through food dye and regret. This one does it with a flower. Butterfly pea flower, brewed across South East Asia as a vivid blue tea, owes its colour to anthocyanins, the same family of pigments that colours blackberries and red cabbage.
Anthocyanins are natural pH indicators. In a neutral liquid they hold a deep blue; as the liquid turns acidic their molecular structure changes and the colour moves through violet towards pink. Stirred with gin and syrup, the drink stays blue because nothing in the glass is acidic enough to disturb the pigment. The lemon, arriving later, changes that in seconds. Nothing is hidden anywhere: the same chemistry is what turns red cabbage pink in a pan of vinegar, and it works every time the acid meets the glass.
The Two-Stage Pour
The drink is built in two parts and the second part belongs to the table. Stir the gin and butterfly pea syrup over ice until properly cold, then strain into a chilled coupe. It should arrive looking finished: still, deep blue, faintly sweet on the nose and giving nothing away.
The lemon juice and elderflower liqueur wait in a small jug beside it. Poured slowly over the surface, the acid drags the colour from blue through violet as it sinks, and one gentle stir settles the glass to its final shade. Pour it where the drinker can see it happen. The change occurs once per glass and it is the whole reason the glass exists.
The Syrup
Butterfly pea syrup is a ten-minute job. Steep a tablespoon of dried butterfly pea flowers in 200ml of hot one-to-one sugar syrup for ten minutes, then strain and cool. The flowers give colour and very little else, which is what the recipe wants: the flavour comes from the gin and the elderflower.
Dried flowers are sold online, in Asian grocers and in speciality tea shops, and a small bag will colour a whole season of parties. The finished syrup keeps for a fortnight in the fridge. Steeping longer produces a darker blue rather than a stronger flavour, so err towards more flowers rather than more time.
What It Tastes Like
Underneath the performance sits a light, floral gin cocktail. The syrup brings sugar without much character, the elderflower liqueur adds orchard perfume and a little weight, and the late lemon sharpens whatever it touches, so the first sip after the pour is brighter than the nose suggests.
Anyone wanting more bite can push the lemon to 25ml. The colour change simply becomes more emphatic, because the acid is doing both jobs at once.
How to Serve It
This is a table serve, so treat the second pour as part of the drink rather than an afterthought. Chill the coupes, keep the citrus jug cold, and pour it in front of the person drinking it. For a party, stir the blue stage in a batch, hold it in the fridge and line up one small jug per glass.
An alcohol-free version swaps the gin for tonic water or a non-alcoholic spirit and the liqueur for elderflower cordial; the chemistry neither notices nor cares. Halloween has first claim, but any dinner that needs a conversation restarted will take it gladly.
The Spirit
GinA flavour requirement rather than a method. The law asks only that juniper be the predominant taste and that the spirit reach 37.5%, which leaves everything else on the botanical bill to the distiller and permits a gin that was never redistilled at all.
Frequently Asked Questions
Why does the Witch’s Brew change colour?
Butterfly pea flowers contain anthocyanins, natural pigments that act as pH indicators. In the neutral gin and syrup mix they hold a deep blue; when the lemon juice lowers the pH, their structure changes and the colour shifts through violet towards pink. It is straightforward chemistry, not colouring.
Where do I buy butterfly pea flowers?
Dried butterfly pea flowers are sold online, in Asian grocery stores and in speciality tea shops. Steep a tablespoon in 200ml of hot one-to-one sugar syrup for ten minutes, strain, and the syrup is ready. It keeps for around two weeks refrigerated.
Can I make an alcohol-free Witch’s Brew?
Yes. Swap the gin for tonic water or a non-alcoholic spirit and the elderflower liqueur for elderflower cordial. The colour change works identically, because the acid and the pigment are doing the work rather than the alcohol.
Does the gin choice matter?
Use a classic London dry. The colour work does not care what is in the bottle, but the drink does: a juniper-forward gin gives the elderflower and lemon something to push against, where a soft contemporary gin leaves the glass sweet and slightly shapeless.
Master the Techniques
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Where this one sits
Recipe by Jerry Can Spirits
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