Whipped cream

Why

Cream can be whipped thanks to its fat globules: whipping damages their coating, and the partly solid globules link up into a network that surrounds the air bubbles and holds them in place (partial coalescence). That takes enough fat – Czech whipping cream (smetana ke šlehání) must by law contain at least 30 %, in shops it is usually 30–36 %, whereas thinner cooking cream won't hold a firm foam. The fat has to be partly solid, which is why well-chilled cream straight from the fridge is whipped; in warm cream the fat is liquid, the globules merge instead of holding a network, and the foam is runny or doesn't form at all. If you keep whipping past stiff peaks, the globules clump into lumps of butter and liquid buttermilk separates out: the cream first turns grainy, then falls apart.

How to do it

• Whip cream with at least 30 % fat straight from the fridge; in a warm kitchen chill the bowl and whisk beforehand too.
• Whip at medium speed and slow down towards the end, as the foam stiffens quickly.
• Stop as soon as the peak on the whisk holds its shape: soft peaks for creams, stiff foam for cakes and piping.
• Fold whipped cream into a cream mixture gently with a spatula, in portions, so it keeps its air.
• Keep finished whipped cream in the fridge and use it within a few hours; it gradually slackens and weeps.

If it goes wrong

Slightly overwhipped, grainy cream can often be saved: fold in a few spoonfuls of cold liquid cream with a spatula until it turns smooth again. Once butter and buttermilk have separated, it won't become whipped cream – whip the butter all the way, pour off the buttermilk and use the butter for baking. Cream that refuses to whip should go into the fridge together with the bowl for 15–20 minutes before you try again.