In a large pitcher, muddle 1 cup fresh mint leaves, 2 quartered limes and 3/4 cup fresh lime juice with the back of a spoon. Stir in 1/2 cup plus 2 tablespoons confectioners' sugar and 1 tablespoon plus 1 teaspoon unsulfured molasses. Add 4 cups seltzer. Serve, unstrained, over ice.
