How we tested
Treacle is sugar cane syrup, a British staple that most sources say is similar to molasses or corn syrup. There are two types of treacle: light (known more commonly as golden syrup) and black. We purchased both and made tarts with these British ingredients as well as with molasses, light corn syrup, and dark corn syrup. Tasters overwhelmingly praised one of the tarts for its “nice sweetness and flavor.” The other, however, was universally panned as “bitter,” “brutal,” and “burnt.” Both light and dark corn syrups were found to be suitable substitutes for golden syrup (and can be used in the same ratio), but molasses had a strong “malty” flavor that tasters rejected.