Scoop the pumpkin purée onto a few layers of paper towels and allow to sit for a few minutes to draw out the moisture. In the meantime, preheat the oven to 325℉ and line a baking sheet with parchment paper. Set aside.
With another clean paper towel or thin tea towel, gently wring the pumpkin purée to squeeze out any excess moisture—be careful, as the paper towel can tear. If at any point the paper towel becomes too weak, transfer the pumpkin purée to another clean paper towel and continue this process. Once finished, the pumpkin should be dry and malleable, around ½ it's original volume.
To a large mixing bowl, add the drained pumpkin purée, maple syrup, and olive oil. Whisk vigorously until the mixture is homogeneous—it may take a few minutes to get rid of any clumps of pumpkin.
Once mixed, add in the oats, pecans, pepitas, quinoa, chia seeds, pumpkin pie spice, and salt. Stir with a spatula until evenly combined.
In a small bowl, whisk the egg white until slightly frothy and broken up, about 1-2 minutes. Add the egg white to the granola mixture.
Stir the granola until well combined, then pour it onto the prepared baking sheet. Firmly press the mixture into an even slab ¼ to ½ inch thick.
Bake the granola for 30-35 minutes, until crisp and golden around the edges. To test it for doneness, open the oven and carefully pinch a bit of granola off of the pan. Let it cool. If you taste it and it's too soft, continue to bake until crisp to your preference.
Remove the granola from the oven and allow it to cool completely before breaking it up into pieces (the size is up to you). Store the granola in an airtight container for 1-2 weeks.