What to put in a hot chocolate, and when to put it in

SALT. A pinch, well below the level at which it registers as salty. Sodium suppresses bitterness perception at low concentrations — a well-documented interaction, and the reason salt turns up in caramel, in coffee and in tonic water. Suppressing the bitterness lets sweetness and the cocoa's aroma through, so the drink reads as more chocolatey and slightly sweeter without either having increased. It is the highest-return addition available and it is free.

VANILLA. A few drops of extract, or a pod infused into the milk. Vanillin occurs in cocoa's own aroma profile, and the combination has been so thoroughly learnt — every mass-market chocolate in the world contains vanilla or vanillin — that added vanilla is perceived as MORE CHOCOLATE rather than as vanilla. That is a learnt association rather than a chemical one, and it is strong enough that blind tasters routinely describe the vanilla-boosted sample as better chocolate.

Both are effectively invisible when correctly dosed. If you can taste the salt or identify the vanilla, there is too much of each.

CINNAMON is the traditional partner across the Mesoamerican and Iberian world, and the association is centuries old rather than a modern flavouring. Cassia is the sharp, sweet, familiar one; true cinnamon is more floral and less aggressive. Ground goes in with the cocoa; a stick infuses into the hot milk for a few minutes and gives a cleaner result.

CARDAMOM brings a resinous, faintly citrus, cooling quality that cuts richness. Crush the pods and infuse; ground cardamom loses its volatile character quickly and is a much weaker version of itself.

NUTMEG in a very small quantity adds a warm, slightly sweet depth. It is easy to overdo and it does not take much to make a drink taste of eggnog.

GINGER, fresh, sliced and infused, gives heat and a bright edge that works particularly well with dark chocolate. Ground ginger is a different and more muted flavour.

CLOVES are powerful and should be used in ones. A single clove in a pan of milk is enough.

STAR ANISE has a natural affinity with dark chocolate's own aniseed-adjacent notes, and one point of a star is plenty.

Chilli in chocolate is the oldest documented flavouring in the subject — chilli appears alongside cacao throughout the Mesoamerican record, long before sugar did — and it is worth understanding that it is not a flavour in the ordinary sense.

Capsaicin binds to a heat receptor rather than to a taste receptor, so what it adds is a sensation running alongside the flavour rather than a note within it. That is precisely why it works with chocolate: it does not compete for the same perceptual space. It also arrives late, building over several seconds and lingering, which is why a chilli hot chocolate tastes like ordinary hot chocolate for the first moment.

Capsaicin is fat-soluble, so a rich drink carries it further and more slowly than a thin one, and the same quantity is much hotter in a water-based drink than in a creamy one. Infuse a dried chilli in the milk and remove it, tasting as you go; ground chilli is irreversible and grainy.

ORANGE is the classic and the mechanism is worth knowing: the aroma lives in the peel oil, not the juice. Juice adds acid, which can curdle milk and dilutes the drink. A strip of zest infused in the hot milk, or a little grated zest, delivers the aroma with none of the acid. The same applies to lemon and to bergamot.

MINT is best as fresh leaves bruised and infused; peppermint extract is much stronger, much sharper, and very easy to overdo into toothpaste. Menthol produces a cooling sensation by the same receptor mechanism that chilli uses for heat, running in the opposite direction.

COFFEE — a spoonful of espresso or strong coffee — deepens a hot chocolate without making it taste of coffee, because the two share roast-derived aroma compounds. Past about a shot it becomes a mocha, which is a different drink with its own page.

ROSE AND ORANGE BLOSSOM WATER belong to the eastern Mediterranean and Middle Eastern tradition and are used in tiny quantities. A few drops; more reads as soap.

CARAMEL brings its own bitterness alongside sweetness, which is why salted caramel and chocolate work so consistently — both sides are bitter-sweet rather than merely sweet. A spoonful of caramel sauce stirred in is the practical route; caramelising sugar into the pan before the milk goes in is better and much more trouble.

HAZELNUT AND PISTACHIO work through roast-aroma overlap, the same mechanism that makes coffee work. A spoonful of nut paste or good nut butter whisked into the hot milk before the chocolate gives a far better result than any flavouring syrup, and it also thickens the drink slightly.

TAHINI is the addition most people have not tried and the one most worth trying. Sesame is roasted, so it shares the roast aroma family; it is also bitter and savoury, which cuts sweetness rather than adding to it. A teaspoon in a mug transforms a milk chocolate drink.

COCONUT, as coconut milk replacing part of the dairy, brings its own fat and a distinct sweetness. Note that coconut fat is highly saturated and sets firm, so a coconut hot chocolate thickens noticeably as it cools.

MALTED MILK POWDER shares Maillard-derived aroma families with cocoa, which is why malt and chocolate taste like one thing rather than two. It also brings body from its milk solids and flour.

INFUSE anything whose flavour lives in a volatile oil held inside solid plant material: whole spices, citrus zest, fresh ginger, mint, coffee beans, vanilla pods, chillies. Warm them in the milk, hold below a simmer for a few minutes, strain, then make the drink. Infusion extracts more and gives a cleaner texture than grinding.

STIR IN anything already dispersed or dissolved: extracts, ground spices, nut pastes, tahini, caramel, malt powder, salt, sugar. Ground spices are best added with the cocoa so that they wet at the same time.

FLOAT anything meant to be a contrast rather than part of the drink. Whipped cream is a temperature and texture contrast as much as a flavour one. Marshmallow melts into a sweet foam that changes the top few centimetres and nothing below. Grated chocolate on cream stays crisp for a minute or two and then does not. A dusting of cocoa or cinnamon on foam delivers aroma directly to the nose on the first sip, which is more of the point than it sounds.

AND ADD ONE THING AT A TIME. A drink with cinnamon, chilli, orange and vanilla in it tastes of none of them.