Soak the cashews for several hours, preferably overnight, until they have softened, and become plump.
Drain, and place into a high-speed blender or food processor, along with the plant milk, lactic acid, and olive oil. Blitz until smooth and creamy, scraping down the sides of the jar/bowl as necessary.
If you want, add a little sea salt, blitz, taste. Add more if necessary, little by little, tasting as you go. The aim is just to enhance the overall flavour, not to create any saltiness.
Store in an airtight jar in the 'fridge for up to a week.
If you're in a hurry, instead of soaking the cashews, boil them for 20 minutes, then cool under cold running water.
Re. plant milks, I find it's best to use one that's as bland as possible, and with no added gums, fillers, or flavourings. Using cashew milk is a no-brainer, of course but plain soy works really well too (obviously not suitable for people who are allergic or sensitive to soy). I don't recommend coconut milk, due to its flavour, and rice milk tends to be a bit too sweet. Of course, you may feel differently!
Re. sea salt, I added ⅛ teaspoon to start with but found that a little more was needed, so I added another couple of pinches.
Nutritional data does not include salt because I have no way of knowing how much you'll be using.
Prep time does not include soaking of the cashews.
If you don't have any lactic acid, you could use lemon juice, apple cider vinegar, or citric acid - but add a little at a time, until you get the right flavour.
The lactic acid I use comes from sugar beets and/or sugar cane, and is certified vegan.