The night before take the phyllo dough out of the freezer and let thaw. Do not open it until you are ready to make your spanakopita
Soak cashews with boiling water for 30 mins.
Once cashews have softened, in a high speed blender blend together cashews, oregano, nutritional yeast, non-dairy milk and a pinch of salt. Pour mixture into a container and stick in the fridge to thicken, for an hour or so. You can make this the night before as well.
When cashew cheese is cooled, add to a mixing bowl. In a sauté pan, heat olive oil and add leeks and cook until they are soft. In the last two minutes of cooking, add the spinach and cook just until it is wilted. Add this to the cashew cheese, as well as the chopped dill and a pinch of salt. Mix to combine
Preheat oven to 375
Unroll the phyllo dough carefully. Take one phyllo sheet and sprinkle olive oil all over the sheet. Fold in thirds. In the corner of the folded phyllo add a tbsp of cashew mixture holding the corner bring to opposite end in a triangle, and fold into triangles as you go along.
Once you have used all of the mixture, brush spanakopita with olive oil or melted butter. Bake until they brown, about 15-20 minutes