A traditional Fool is made with generous amounts whipped heavy cream with fruit gently folded in. This lighter alternative uses sour cream and yogurt and originated in Cooking Light. I have adapted it a bit to my own tastes and preferences.
Combine strawberries and granulated sugar in a large bowl. Cover and chill 2 hours.
Combine brown sugar, confectioners sugar, vanilla extract and yogurt and sour cream in a blender. Blend for a minute or two so that the sugars are blended in and you have incorporated a bit of air in the dairy mix. (i've also done this with an immersion blender.) Turn out into a covered bowl and chill for 2 hours.
Just before serving, gently fold the strawberry mixture into the yogurt mixture until swirled.