Making liqueur involves starting with a base alcohol, adding ingredients for flavoring and filtering the liquid. For example, soak ground star anise in vodka for two weeks, filter out the spice, and dissolve 1 cup of sugar in the alcohol to make a liqueur similar to Sambuca.
The first step to making liqueur is preparing the infusion ingredients ahead of time. For instance, fruit liqueurs call for rinsing and cutting the target fruit into small pieces. For coffee liqueur similar to Kahlua, prepare a batch of cold-brewed coffee and add brown sugar simple syrup.
Next, place the ingredients in a glass jar or bottle, and pour the base alcohol over the top. Base alcohols are vodka, rum, cognac and brandy. Fruit is usually steeped in vodka or grain alcohol. For coffee liqueur, use aged rum. Seal the container, and place it in a cool, dark location.
The liqueur typically needs to steep for two to four weeks, with longer times yielding a stronger flavor. Most recipes call for taste testing along the way.
Filtration is a three-stage process. Set up three grades of filters over containers for the alcohol. Start with the coarsest filter, slowly pouring the alcohol through to remove the flavoring ingredients. Repeat with the other two filters, working to the finest mesh. Add a sweetening agent such as simple syrup or honey, and age in a sealed container for at least a few weeks.