Which mixing behavior can cause a ganache to break?

Excessive agitation when cold is a critical factor that can lead to a ganache breaking. Ganache, which is an emulsion of chocolate and cream, relies on a delicate balance of fat and liquid. When ganache is cold, the cocoa butter in the chocolate hardens, and vigorous mixing can cause the emulsion to separate. The mechanical action from excessive agitation disrupts the stabilized system, preventing the fat and liquid from combining properly, hence resulting in a broken or grainy texture instead of a smooth ganache.

In contrast, infrequent stirring might not provide enough agitation to create a homogeneous mixture but generally wouldn't break the ganache. Mixing at room temperature is usually done to maintain a stable emulsion, and gentle folding helps maintain integrity without introducing excess air or breaking the emulsified mixture.