Soak cashews in very hot water for 1 hour or in cool water for 6 hours or overnight. Drain.
Add drained cashews to a high-speed blender with water and blend until creamy and smooth, scraping down sides of blender as needed.
Scrape mixture into a mixing bowl and add contents of probiotic capsules. Stir with a wooden or plastic spoon (not metal as it can react with the probiotics) until fully incorporated.
Cover with a piece of cheesecloth or a very thin towel and secure with a rubber band. Let rest on the counter (preferably in a room warmer than 70 degrees F (21 C)) for at least 24 hours or up to 48 hours. The longer it rests, the thicker and tangier it will become. We found 48 hours to be the sweet spot.
Once the mixture has reached your preferred tanginess and texture, uncover and add the salt, lemon juice, and apple cider vinegar. Stir thoroughly to combine.
Taste test and adjust as needed, adding more lemon juice for acidity, salt for saltiness, or apple cider vinegar for tanginess.
Use immediately, or for cold sour cream, chill at least 6 hours. Will keep covered in refrigerator for 5 days, oftentimes longer. You'll know it's gone bad when mold has formed or it no longer smells and tastes appetizing.
*For probiotics like Renew Life 50 billion and Jarrow // make sure your probiotics don’t contain PREbiotics or the recipe won’t work. Also use capsules as opposed to tablets, which are not as high quality and need to be crushed.*One probiotic capsule (emptied) should measure about 1/3 tsp probiotic powder.*Prep time reflects a 1-hour quick soak for the cashews, 30 minutes prep for adding probiotics and lemon (etc.), and a 48-hour culturing period.