Pour all ingredients except lemon smile into cocktail shaker filled with ice. Shake hard for 15 seconds and double strain into a coupe glass.
To make a lemon smile, peel a large swath of lemon and use your paring knife to scrape away any white pith inside. Clean up the edges and cut into a long diamond with a slice lengthways down the center.
Combine ingredients in small saucepan. Bring mixture up to 170 degrees and cook for about 15 minutes, or until the blackberries have released their juice and the sugar has dissolved. Strain out the solids.
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