Extract/partial mash sours

How can one make a sour from extract/partial mash? If i understand correctly sour beers need alot unconverted starches from a turbid mash.

They don’t need unconverted starches. One thing those unconverted starches allow for is food for brettanomyces that can’t be eaten by saccharomyces. Steve Piatz of MN is a nationally award winning lambic homebrewer who makes extract beers. Check out Northern Brewer’s extract kits and watch Brewing TV’s expisode 49.

I watched that episode on my lunch break at work today. Really informative and got me interested in brewing a sour.