Erin Mann’s family holiday tradition of making toffee sometimes hits a snag. The Chicago resident says that at some point during cooking, the toffee has a tendency to separate into an oily mess. She wanted to know why and how to fix it.
Toffee is an emulsion of fat and sugar that is cooked to 285°F to 290°F, which triggers the Maillard browning reaction that gives the candy its caramel color and flavor. It also is notoriously finicky. That’s because traditional toffee recipes often call for sugar and butter in equal amounts. Most butter predominantly is made up of fat and water, and the two easily separate when heated. For toffee, that can be a problem. If the water simmers off too quickly, the emulsion of sugar and fat will break, says baking expert Stella Parks in her book “BraveTart.” During cooking, several factors can affect the stability of the emulsion. Fluctuating temperatures, not stirring enough (or conversely, overworking the mixture), using thin-bottomed pans, even ambient humidity all can lead to toffee that splits. Luckily, Parks has a simple solution: Replace the butter with heavy cream. Cream itself is an emulsion—a stabilized one. That is, unlike butter, cream won’t separate when heated. This extra stability helps prevent the toffee from breaking when cooking. “The Joy of Cooking” also takes this approach with its English toffee recipe, which relies on both butter and cream. In our testing, we found that replacing half of the butter with cream produced delicious toffee that stayed perfectly emulsified, every time.