Which ingredient is commonly found in a mocha?

A mocha is a popular coffee beverage that combines espresso, steamed milk, and chocolate, typically in the form of chocolate syrup or cocoa powder. The distinctive flavor of a mocha comes primarily from the chocolate incorporated into it, making chocolate syrup a key ingredient. This ingredient not only adds sweetness but also rich chocolate flavor, which balances the bitterness of the espresso and the creaminess of the milk.

The other options—vanilla extract, maple syrup, and strawberry puree—are ingredients that may be used in other drinks or desserts but are not traditional components of a mocha. Vanilla extract is often associated with vanilla lattes, maple syrup might complement flavors like pecan or butterscotch, and strawberry puree would likely be found in fruit-based drinks rather than in a mocha. Therefore, chocolate syrup is the correct choice as it is central to the defining characteristics of a mocha.