In a mixing bowl, whisk together the oat flour, cassava flour, potato starch, and white rice flour. Add the plant-based milk, olive oil, maple syrup, and salt. Whisk until smooth and no lumps remain. Let the batter rest for 10 minutes.

Heat a nonstick skillet over medium heat and very lightly coat with vegan butter or oil. You are not looking for more than a just barely oiled pan surface here. Pour a small amount of batter into the skillet or crepe pan, swirling to spread it into a thin, even layer that reaches the edges of the pan. The exact amount of batter will depend on your pan, but for normal size blintzes this should be between ¼-⅓ cup.

Cook until the edges lift slightly and the bottom is golden brown, 1-2 minutes. Flip and cook for another 30-60 seconds. Transfer to a plate and repeat with the remaining batter, adding more butter or oil as needed.

For the kasha and fried onion filling, warm a pan over medium heat. After 90 seconds when the pan is hot, add the minced garlic to the dry pan and cook for 30 seconds until fragrant. Stir in the kasha, salt, black pepper, and thyme. Toast for 1 minute, stirring frequently. Pour in 1 ⅓ cups of water and bring to a boil. Reduce to a simmer, cover, and cook for 10-12 minutes, until the liquid is absorbed and the kasha is tender. Remove from heat and let rest for 5 minutes before fluffing with a fork.

In a separate pan, heat the remaining olive oil over medium heat. Add the chopped onions and cook, stirring occasionally, until deeply golden brown, 15-20 minutes. Stir the caramelized onions into the cooked kasha.

For the sweet cheese filling, pour boiling water over the cashews in a heat-proof bowl and let them soak for at least 20 minutes. Drain and rinse the cashews.

Blend the tofu, drained cashews, agave nectar, plant-based yogurt, rice vinegar, white miso paste, vanilla extract, and salt in a food processor until completely smooth, scraping down the sides as needed.

To assemble, fill each crepe with the desired amount of kasha and fried onion filling or sweet cheese filling. Fold or roll the crepes and serve immediately with apple sauce and vegan sour cream. Optionally you can pan fry the stuffed blintzes in vegan butter on a couple of sides before serving.