1) Dissolve the meringue powder in the lime juice. Fill a cocktail shaker with ice.
2) Add the meringue mixture, pisco, simple syrup and bitters to the cocktail shaker. Cover and shake vigorously until frothy, mixed and chilled, about 45 seconds.
3) Strain into a glass and garnish with grated zest or a wedge of lime.
For the simple syrup:
1) Put the sugar and water in a small saucepan.
2) Cook over low heat, stirring, until the sugar dissolves. (Alternatively, heat in the microwave.) Store in a sealed container in the refrigerator for up to 1 month.