Preheat your oven to 325°F and line a large rimmed baking sheet with a piece of high-quality parchment paper.
In a large mixing bowl, whisk together the liquid egg whites, unflavored whey protein isolate, and nutritional yeast until the mixture is completely smooth and free of any protein powder clumps.
Fold in the pumpkin seeds, sunflower seeds, chia seeds, garlic powder, onion powder, sea salt, and black pepper until the seeds are evenly distributed throughout the batter.
Pour the batter onto the prepared baking sheet and use a spatula to spread it into a very thin, even layer that reaches the edges of the pan.
Bake for 20 minutes until the edges are golden brown and the center of the sheet feels firm and dry to the touch.
Carefully remove the sheet from the oven, flip the entire crisp over (you may need to break it into two large pieces to do this easily), and bake for an additional 5 to 7 minutes until brittle.
Transfer the baked sheet to a wire cooling rack and let it sit for at least 10 minutes to allow the crisps to fully harden and reach maximum crunch.
Break the large sheet into individual shards and serve immediately or store in an airtight container for later snacking.