1 Rinse raspberries and blueberries and drain well. Squeeze juice from lemon. Mix yogurt, sour cream, 3 tablespoons lemon juice and powdered sugar in a bowl.
2 Whip cream until stiff and fold into yogurt mixture.
3 Puree raspberries with an immersion blender, then puree blueberries. Divide yogurt mixture into thirds. Mix raspberry puree into one third and blueberry puree into another third.
4 Layer three yogurt mixtures in 6 glasses, dividing evenly, and freeze until starting to firm, about 25 minutes.
5 Insert a plastic spoon into each glass and let freeze overnight. To serve, warm up glasses with palm of hand slightly to loosen popsicles from glasses before removing.