In order to FULLY remove alcohol from food when cooking, it needs to simmer for a minimum of three hours. Because this sauce is only cooking for 15 - 20 minutes, about 40% of the alcohol will remain. If you want to cook more of it out - use a WIDE, shallow pan and stir constantly. Stirring helps the alcohol to evaporate, as does a larger surface area. The good news is that whisky does seem to evaporate quicker than most spirits.