If blackberry picking isn’t an option for you, go with the frozen kind, which are preserved when ripe. The blackberries in the produce section tend to be sour and unripe, since a ripe blackberry turns to a mushy purple mess quickly.
I actually prefer the DIY variety to commercial blackberry liqueur (aka creme de mure).
DIY Blackberry Liqueur
2 cups blackberries (defrost first, if using frozen)
3/4 cup brandy
1 1/4 cups vodka
1/2-inch piece of lime zest without pith (optional)
1 cup simple syrup (equal parts sugar and water)
In a sealable glass jar, muddle the blackberries and lime zest lightly to release juice and then add brandy and vodka. Seal and shake. Steep for 3 days, then strain through a fine mesh strainer, pressing down to extract juice. Filter through a coffee filter or two layers of cheesecloth.
Add simple syrup to the strained infusion and shake in sealed jar. Let rest for one day before use.
The recipe I developed and posted here was first published on Serious Eats.