In a large, microwave-safe bowl combine the cereal, pretzels, and nuts.
In a separate bowl, whisk together the melted vegan butter, tamari, miso, garlic, and onion powder.
Drizzle half of the butter mixture over the cereal and gently stir to combine. Then pour in the remaining butter mixture and again, stir the cereal to ensure it's all coated.
Place the bowl in the microwave and cook on high for 6 minutes, removing the bowl and stirring every 2 minutes.
When it's done, let it sit for a minute, then pour it onto a pan lined with parchment or waxed paper. Use a spatula to spread it out into a thin layer. The cereal will get crunchy as it cools.
Transfer to a serving bowl to serve. Store in an airtight container for up to 15 to 20 days.