Butter Scotch Candy

The vinegar serves a crucial role by inverting some of the sucrose into glucose and fructose, preventing premature crystallization that would make the candy grainy. Brown sugar's molasses content provides deep flavor and helps control crystal formation. Butter, added after initial cooking, contributes fat that creates a smooth texture and prevents the syrup from seizing. Slow boiling without stirring allows the mixture to reach the hard crack stage (300-310°F) while minimizing crystal formation along the pan sides.