Soft peaks is a cooking term you may come across when making both dessert and savoury dishes. They refer to a protein structure that surrounds a pocket of gas in foams made of egg whites or cream.
What does this mean to the average home cook?
These pockets of gas, most often simply oxygen, are the key to lightness - whether it is the lift for a soufflé, the rise in a flourless cake, or simply the softly whipped cream you serve along side a dessert
Soft peaks are one step below the cooking stage of stiff peaks. When you beat either egg whites or cream, air is incorporated into a fat and protein structure. This "trapped" air can be harnessed most effectively to give lift to cakes, meringues, soufflés and even simple whipped cream to accompany your dessert dish.
If a recipe calls for soft peaks to be beaten from either cream or egg whites here is how to go about the procedure, and how to tell when it is done. Ideally use a Mixmaster, or failing that, a stainless steel or glass bowl and a hand-held balloon whisk. Whisk the cream or egg whites until they have turned opaque and have begun to hold their own shape. This is the key to soft peaks - You don't want to over beat them. Soft peaks will gently fall back upon themselves when they are just right. Test and see, lift the whisk out of the cream or whites right through the top of the mixture. Soft peaks will gently fall back upon themselves, while stiff peaks will gallantly hold their shape.
Soft peak foams, whether they be egg white or cream based are generally used not so much for their rising capacity, but for their ability to give a lightness to a more dense mixture - such as a thick cheese sauce for a soufflé, a rich couveture based cake, or a dense crème patissiere.
If you need soft peaks in a recipe - cream or egg; and you accidentally over beat the mixture, simply place it in a refrigerator for 15 minutes to let the proteins settle. You can gently whip the mixture again close to serving time to attain its former soft peak glory