Heat the oven to 300°F (150°C) and line a large sheet pan with parchment.
In a large bowl, mix the oats, nuts, seeds, cinnamon and salt.
Whisk the maple syrup, oil and vanilla, pour over the dry mix, and stir until everything is coated. Fold in the frothy egg white, if using.
Spread the mixture evenly on the pan and press it down firmly with a spatula.
Bake for 40–45 minutes, rotating the pan halfway, without stirring, until golden and fragrant.
Let it cool completely on the pan (it crisps as it cools), then break it into clusters and mix in the dried fruit.