Preheat the oven to 325 degrees F. Line a large rimmed baking sheet with a Silpat baking mat or parchment paper. Set aside.
In a large bowl, combine the oats, nuts, coconut flakes, cocoa, sugar, espresso powder, and sea salt.
In a medium bowl, stir together the melted coconut oil, maple syrup, and vanilla extract.
Pour the liquid ingredients over the dry ingredients and stir with a rubber spatula until well combined.
Pour the oat mixture onto the prepared baking sheet, spreading it out in an even layer. Bake for 20 minutes and then stir. Bake for 5 to 10 more minutes or until granola is golden. It is hard to tell because of the cocoa powder, so check early, you can take a little off the pan and test it. The granola will crisp up as it cools.
Remove the pan from the oven and let the granola cool completely. DO NOT STIR while it is cooling. When completely cooled, you can stir in chocolate chips, if using. Enjoy with yogurt, milk, or by the handful.
The granola will keep in a sealed container or glass jar for up to one month in the pantry.