Blend or whisk the yogurt with ¼ c water, oil, and salt, until smooth.
Pour into container, cover, and let sit at room temperature for 8 to 24 hours. Longer culturing = sharper cheese.
Measure tapioca and xantham into the bowl and set next to the stove alongside the cultured cheese.
Place remaining ½ c of water in the saucepan over medium-low heat and slowly add the agar, whisking constantly until you have a thick paste, about 2 minutes. If it seems very dry, add a tiny bit more more water, 1 t at a time.
Slowly pour in the cheese, whisking constantly. When the mixture is hot and smooth, trade the whisk for the wooden spoon.
Gradually add the tapioca, stirring constantly. If the mixture starts to boil, reduce the heat. You want it to be very hot without actually boiling.
Continue cooking and stirring until the mixture thickens and starts to look glossy, 3-5 minutes.
Use immediately as a sauce or spread into the container and let cool, then refrigerate for at least 3 hours. It will last around 2 weeks in the refrigerator as long as it’s properly sealed.