Place the first seven ingredients in a wide pot. Simmer a few minutes over medium-low heat until the sugar is dissolved; cool to room temperature. Line 4, 6- to 8-oz. ramekins with plastic wrap. Cut out rounds of bread the same size as the bottom, and the top, of the ramekins. Set the bottom bread rounds in the ramekins. Cut the rest of the bread in strips and line the walls of the ramekins; spoon in the berries and their juices about a 1/2 inch over the top. Reserve any leftover berries in the fridge. Set on the top rounds of bread, gently pressing them down to seal in the berries.
Fold over the plastic wrap to cover the puddings. Place on a tray; set another tray on the top and weight to compress the puddings. Refrigerate 4 hours or overnight. To serve, unwrap the plastic and invert the puddings on dessert plates and unmould. Spoon any leftover berries and juice alongside. Garnish with mint sprigs and, if desired, a dollop of lightly sweetened whipped cream.