In a blender, combine 1 pint of blueberries, honey, lime juice, and 5 mint leaves; puree. Press mixture through a fine mesh sieve to remove skin and seeds. Discard skin and seeds. Taste and add more honey if desired. Transfer to a container, cover with plastic wrap, and refrigerate until cold, about 10 minutes.
With an electric mixer or a whisk, whip the cream until it holds stiff peaks. Fold the cream into the yogurt.
Using a light hand, fold the blueberry puree into the yogurt mixture about three quarters of the way, leaving a swirly pattern of dark purple streaks through the white yogurt mixture.
Spoon into 4 glasses and chill. To serve, sprinkle with pistachios, and garnish with remaining blueberries and mint sprigs.