Combine the vodka, lemon juice, ¾ ounce of blackberry simple syrup from above, and the egg white in a cocktail shaker without ice, and shake for 10 to 20 seconds. Hold your shaker tight, because it will try to pop open.
2 ounces vodka, ¾ ounce lemon juice, ¾ ounce blackberry simple syrup, 1 egg white