Ganache and chocolate creams

Why

Ganache forms when hot cream melts chocolate: droplets of cocoa butter and milk fat disperse in the water from the cream, which holds dissolved sugar and suspended fine cocoa particles. The ratio decides the firmness: roughly equal weights of chocolate and cream give a glaze or sauce that thickens as it cools, twice as much chocolate a firm truffle filling, and more cream a soft cream that can be whipped; milk and white chocolate need a larger share for the same firmness because they contain less cocoa solids. If the ganache overheats or has too much fat for too little water, the droplets merge and the fat separates as a greasy layer, much as in hollandaise. If, on the other hand, there is too little liquid for a lot of cocoa solids, the particles soak up the water and the ganache turns grainy and stiff like seized chocolate (Melting chocolate card). Cream ganache is a moist dairy cream, which is why desserts made with it belong in the fridge.

How to do it

• Chop the chocolate finely, heat the cream only to just below boiling point and pour it over the chocolate all at once.
• Leave it for 1–2 minutes, then stir with a spatula in small circles from the centre until a glossy core forms, gradually drawing in the edges.
• A stick blender gives a reliably smooth ganache if you keep its head fully submerged so it doesn't whip in air.
• Use ganache lukewarm and flowing for glazing, let it thicken at room temperature for no more than 2 hours for filling cakes, and chill it in the fridge for whipping.
• Whip chilled ganache only briefly to a paler cream; long whipping makes it grainy, like over-whipped cream (Whipped cream card).
• Keep desserts with ganache covered in the fridge and let them soften briefly at room temperature before serving.

If it goes wrong

A greasy, split ganache is rescued with a spoonful or two of warm milk or cream: stir it into the centre, or blend the ganache with a stick blender until it comes together again. A grainy, stiff ganache is fixed the same way, just with more liquid, a spoonful at a time. If the ganache split while chilled, first warm it gently over a bain-marie until it starts to melt at the edges, then blend. Thicken a runny ganache with melted chocolate, loosen a stiff one with warm cream.