Creme de cassis flavors the kir royale, the Parisian martini, the El Diablo and the Londoner. A liqueur traditionally made from black currants, sugar, water and a neutral liquor, creme de cassis is simple to make at home. Start the process 10 days or more before you plan to use or gift the liqueur to allow the currant’s flavor to fully infuse the alcohol. Keep homemade creme de cassis tightly covered in the refrigerator for approximately three months.

Prepare the Currants

Use fresh ripe currants, if possible, although you can substitute frozen, thawed currants with good results. The black currants typically used in creme de cassis peak during June, July and August. You can also make the liqueur with red currants, available during the winter, or use a combination. Wash the currants, drain them of excess water and place them in a large bowl. Use a potato masher to smash the fruit into a thick, pulpy mass.

Add the Alcohol

You can use any 80- or 100-proof spirit to make creme de cassis, though vodka is the most common choice. Don’t worry about using an expensive brand, says The Kitchn recipe editor Emma Christensen, since the finished liqueur tastes more of fruit than alcohol. A basic, low- to medium-priced liquor is OK. Stir the alcohol into the mashed currants, using approximately one 750-milliliter bottle for every 3 cups of fruit. You can do this in the bowl you mashed the currants in or transfer the fruit to a large glass jar first.

Leave It to Infuse

Put plastic wrap over the bowl, or screw the lid onto the jar and let the mashed currant and alcohol mixture sit at room temperature for 24 hours out of direct sunlight. Stir and mash the currant and alcohol mixture a few more times, then recover the bowl or replace the lid and put it in the refrigerator. The length of time it spends in the fridge determines the strength of the finished liqueur’s fruit flavor. Three days of refrigeration provide a mild currant taste, while seven to 10 days yield a liqueur with a pronounced berry flavor.

Strain and Sweeten

When the mixture infuses sufficiently to give the alcohol the amount of fruit flavor you want, pour it through a fine-mesh sieve lined with cheesecloth. Transfer the thick, red liquid to a glass jar. Make a simple syrup by dissolving one part sugar in two parts boiling water. Let the syrup cool, then add it to the currant-alcohol liquid, stirring thoroughly. Taste the liqueur and add more simple syrup if you want it sweeter; add water if it’s too strong or alcohol if it isn’t strong enough.