A delicious, creamy vegan tzatziki sauce made with the magic of cashews. Note that the sauce is best when refrigerated overnight, so factor that into your prep time. Goes great on gyros, and as a veggie dip or salad dressing.
Place the cashews in a small bowl and cover with water by 1/2". Let soak for an hour, then drain, discarding the soaking liquid.
While the cashews soak, peel the cucumber and remove the seeds (slice the cucumber in half length-wise, and cut a "V" around the seed bed). Grate the cucumber on a box grater, and transfer the grates to a sieve set in a bowl. Press the cucumber grates with a paper towel, and let drain until ready to use, discarding the cucumber liquid.
Add the drained cashews and 1/2 cup water, lemon juice, vinegar, and garlic to a high-performance blender, and blend. Stop after 30 seconds, and check the mixture. If it's thick and grainy like paste, add a tablespoon of water, and blend for another 30 seconds. Check again. Add another tablespoon of water, if necessary, and blend. The sauce should creamy-smooth.
Scrape the sauce into a bowl, and stir in the drained cucumbers, herbs and salt. Cover, and refrigerate overnight or at least 6 hours. Taste. Add a pinch more salt for a pop of flavor, and/or a small splash of lemon juice for additional tang.