Using a 3 1/4-inch round cookie cutter, stamp out a round from each brioche slice. Dip 6 rounds in the berry puree to coat completely; place 1 in each prepared ramekin. Spoon the mascarpone over the rounds, spreading it evenly. Scatter the sugared raspberries on top. Dip the 6 remaining brioche rounds in the remaining puree and place in the ramekins. Fold the overhanging plastic wrap over the top, pressing hard to compact the puddings. Refrigerate for at least 30 minutes and for up to 24 hours.