Purée about one-third of the raspberries in a blender with 1/4 cup of the confectioners’ sugar. Force the purée through a fine-meshed sieve to remove the seeds. Taste; the purée should be quite sweet. If not, add a little more sugar.
Set aside a few berries for garnish and roughly mash the remaining berries just until they’re broken up. Toss with the remaining 1/4 cup confectioners’ sugar.
Beat the cream with the granulated sugar until it holds soft peaks. Fold in the yogurt. Beat in the raspberry purée, then fold in the sugared berries and any juices. Taste and add more confectioners’ sugar if necessary. Garnish with the whole berries and serve immediately. Or cover and refrigerate for no more than 2 hours.