Clean the raspberries well and place in a sterile sealable jar (min 2 cup/480ml volume). Sprinkle the sugar over the top then add the vodka.
Seal the jar then shake well but relatively gently to help the sugar dissolve. Place in a cool dark place for around 2-4 weeks, shaking gently now and then, particularly a couple times in the first day to help the sugar completely dissolve.
Once it has matured, strain the mixture through a fine mesh cheesecloth to remove all solids. Serve as it is (eg chilled) or as a cocktail ingredient.
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Notes
The finished liqueur can be stored at room temperature for a number of months. Once you have made and strained the liqueur, you can add a little extra sugar if you feel you would like it to be sweeter.