What gives butterscotch pie filling its primary flavor?

The primary flavor of butterscotch pie filling comes from brown sugar. Butterscotch, by definition, is a confection that primarily features brown sugar as a key ingredient, which provides its distinctive deep, caramel-like sweetness. When brown sugar is heated, it undergoes a process called caramelization, which enhances its flavor profile and gives butterscotch its signature rich and buttery notes. This foundational element is what distinguishes butterscotch from other sweet flavors in desserts.

While vanilla can enhance flavor and cinnamon may add warmth and spice, they do not contribute the primary flavor profile of butterscotch. Maple syrup, while sweet, introduces a different profile entirely and does not align with the traditional flavor that defines butterscotch. Thus, brown sugar rightfully stands out as the essential flavoring agent in butterscotch pie filling.