Fill a 12-ounce Mason jar with ice. Add the gin and lemonade. Top slowly with the butterfly pea tea—the color will be suspended until you stir it. Garnish with fresh mint and lemon slices, if desired.
Variation: Steep 2 teaspoons of dried lavender in a 750 ml bottle of gin for 24 hours. Strain, and use lavender-infused gin in this cocktail.