1) Preheat oven to 125C/Gas 1/2.
2) Whisk egg white until foamy in a medium bowl. Whisk in sugar, water, salt, cumin, cayenne, garlic and ancho powders. Toss nuts in mixture until well coated.
3) Spray a baking sheet with nonstick cooking spray or line with greaseproof paper. Spread nuts out on the prepared pan in a single layer. Cook for 45 mins until slightly golden, turning nuts with a spatula every 15 mins so they toast evenly and don't stick.
4) Set the nuts aside, stirring periodically as they cool. When completely cool, transfer to serving bowl and garnish with dried red chillis if desired.