How to Make It
Line a 9-inch-square glass baking dish with plastic wrap, leaving enough overhang on all 4 sides to cover the finished pudding.
Place 6 slices of bread in a tight overlapping layer in the bottom of the prepared dish. Place the raspberries, blackberries and currants in a heavy, medium, nonreactive skillet. Add the sugar and cook over moderate heat, stirring occasionally, until they yield some of their juices, about 5 minutes. Sprinkle the kirsch over the berries; remove from the heat.
Using a slotted spoon, spread a third of the berries over the bread in the dish. Cover with another layer of bread. Repeat the layering with the remaining berries and bread. Spoon half of the berry juice over the pudding. Refrigerate the remaining juice. Cover the pudding with the overhanging plastic wrap. Place another dish or pan on top of the pudding and weigh down with some cans. Refrigerate the pudding overnight.
To serve, unwrap the top of the pudding and invert the pudding onto a platter. Cut it into squares. Serve with the whipped cream and reserved berry juice.