Concord Grape Gin Fizz

In a cocktail shaker, muddle the grapes until they've released a deep purple juice. Add the grape juice, gin, port, lemon juice, egg white and sugar and shake vigorously for 30 seconds. Add ice and shake for 1 more minute. Strain into a chilled collins or cocktail glass, top with soda water and garnish with the lemon twist. Serve.