Place yogurt in a strainer lined with paper towel and drain in refrigerator at least 4 hours; discard liquid.
Process half the raspberries in food processor until smooth.
Strain processed raspberries in fine mesh strainer, pressing liquid into large bowl with spatula. Discard seeds.
Whisk in powdered sugar. Stir in remaining berries.
Whip cream with a mixer until soft peaks form. Gently fold in yogurt.
Fold in raspberry mixture.
Chill, covered, at least 1 hour.