Choosing chocolate for frosting

A frosting must be spreadable when applied and must stay pleasant to eat at room temperature. Chocolate sets hard, so the more chocolate a frosting carries, the firmer and less spreadable it becomes as it cools.

That is why high-cocoa-butter couverture — the right answer for coating and moulding — is frequently the wrong answer here. It sets too hard and gives a frosting that cracks when the cake is cut.

For a chocolate buttercream, cocoa powder is often the better choice than melted chocolate: it brings colour and flavour without adding cocoa butter that will set. Dutch-process gives a darker colour and a rounder flavour; natural gives more acidity and lift.

For a ganache-based frosting or a whipped ganache, use a dark chocolate around 55 to 65 per cent, and shift the ratio toward more cream than a coating ganache would use. Higher percentages set harder and need more cream to compensate.

For a fudge-style frosting, an ordinary eating dark chocolate is fine. Chocolate chips are not — they are formulated with less cocoa butter and a stabiliser precisely so that they do not flow, which is the opposite of what a frosting needs.

Setting too hard: too much chocolate or too high a percentage. Add cream or butter, not water.

Splitting or looking grainy: the emulsion broke, usually from adding cold liquid to warm chocolate or from over-beating. Warm a little of the mixture and beat it back in.

Dull and streaky on the cake: the chocolate came out of temper as it set. It does not matter for eating and it is why frostings are textured rather than glossed — if you want gloss, you want a glaze, which is a different preparation.