Melting chocolate

Why

Chocolate is a fine powder of cocoa and sugar, plus milk powder in milk chocolate, dispersed in cocoa butter; a drop of water or steam from a bain-marie dissolves the sugar on the particle surfaces, they stick together and the chocolate seizes into a stiff, grainy paste. A lot of liquid, however, is no problem, because the particles disperse in it – which is why chocolate melts smoothly together with cream. Overheated chocolate thickens, turns grainy and scorches; the Exploratorium advises staying below about 46 °C, and milk and white chocolate are more sensitive than dark because of their milk solids. Cocoa butter sets in several crystal forms and only one gives gloss, snap and melt-in-the-mouth texture, so chocolate that is simply melted and left to set tends to be soft and dull with grey streaks of fat. Tempering, a controlled cooling and gentle rewarming, builds exactly these stable crystals, whereas a glaze made with butter, cream or syrup does not need it.

How to do it

• Chop the chocolate into evenly small pieces and melt it in a dry bowl over hot, not boiling, water without the bowl touching the water.
• In the microwave, heat it at half power in short bursts, stirring in between; residual heat will melt the last pieces.
• Use dry utensils and don't cover the bowl with a lid that drips condensation; add liquid either all at once as the recipe says, or not at all.
• Don't heat dark chocolate above about 46 °C; melt milk and white chocolate even more gently, stirring more often.
• For glossy decorations, temper the chocolate: stir chopped chocolate into the melted chocolate in portions until dark chocolate cools to 31–32 °C; remove any unmelted pieces.
• Make an untempered glaze with butter, cream or hot syrup as the recipe says (Sugar syrup and its stages card, Ganache and chocolate creams card).

If it goes wrong

Seized chocolate is rescued with even more liquid: add hot water or cream a teaspoon at a time, stirring until smooth – it will do for a sauce or glaze, though no longer for tempering or decorations. Pour too-hot chocolate straight into a cold bowl and stir in a handful of chopped chocolate to cool it quickly; once it has thickened and turned grainy it is no good for a glaze, and if it smells burnt, throw it away. Grey streaks on set chocolate are only a cosmetic flaw: eat the chocolate, or melt it again and temper it.