This is a widespread kitchen myth. USDA-funded research and peer-reviewed food science studies consistently show that alcohol never fully evaporates during cooking. Even after 2.5 hours of simmering or baking, approximately 5% of the original alcohol remains. Shorter methods retain far more — flambéing leaves 70–75% intact. Retention ranges from 4% to 95% depending on method, time, temperature, and other factors. The word "completely" makes this claim definitively false.