Drain and rinse the cashews. Combine them with the soaked oats (the oats should absorb the water by now, so no need to drain) and water in an upright, high-speed blender and blend until smooth.
Pour into a glass container, leaving some room at the top for the yogurt to expand. Open the probiotic capsules and pour the powder into the yogurt mixture. Stir with a wooden (or any non-metal) spoon to incorporate thoroughly. Cover the container with a piece of cheesecloth or breathable fabric, fixing it in place with a rubber band (or I use my nut milk bags here) and let culture in a dark place (no direct sunlight), at room temperature for 24 hours.
Taste the yogurt. If it tastes good and yogurt-like enough to you, it's ready. If not, leave it to culture more, for up to 48 hours total. The timing will depend on the temperature in your house and the probiotic you use. Once ready, keep refrigerated in an air-tight container.
Notes
When you are ready to make the next batch of this yogurt, you can save a few tablespoons of yogurt and use it as a starter for your new batch.
Recipe by Golubka Kitchen at https://golubkakitchen.com/easy-homemade-cashew-oat-yogurt/