1. In a small bowl, combine 1/2 cup blackberries and 1 tablespoon sugar. Set aside.
2. In another bowl, combine 2 tablespoons sugar, yogurt, and lemon peel. Gently mix in remaining berries.
3. Spoon yogurt-berry mixture into 4 ovenproof ramekins or bowls, each 1 1/2 to 2 inches deep and 4 to 5 inches wide.
4. In a deep bowl, whip egg whites with a mixer at high speed until foamy. Continue to beat and gradually add remianing sugar (about 1 tablespoon every 15 seconds) until whites hold stiff peaks when beaters are lifted.
5. Swirl meringue equally over yogurt-berry mixture. Set dishes in a 10- by 15-inch rimmed pan. Broil about 4 inches from heat until meringue is browned, 30 to 60 seconds.
6. Spoon reserved sugared berries and their juice over meringues. Garnish with mint sprigs.