Puree the strawberry. Add sour cream, sugar and vanilla extract to the blender and blend well.
Cover and freeze for atleast 4 hours. Then take it out and blend the mixture again until soft. Freeze again for 2 hours. Then break the crystals and blend it again until soft. More beating results in a smoothier and creamier texture.
Repeat a couple of times until it becomes creamy and soft. For the last time alone, do not freeze it, just refrigerate it for best creamy results. Garnish with chopped nuts.