Preheat oven to 375 F. Line a 9x13 pan with parchment paper (if you want easy removal), spray pan lightly with non-stick cooking spray
In a large mixing bowl, add the brown sugar and room temperature melted butter and whisk together well.
Add egg and egg yolk and whisk, then add the vanilla extract and mix again.
Add flour, cocoa powder, baking soda, and salt and whisk together until just combined.
Fold in the coconut, pecans, and chocolate chunks using a rubber spatula.
Transfer to your prepared pan and spread the cookie dough mixture out evenly. You can use your fingers or use the back of the rubber spatula, as the mixture will be thick.
Bake for 20-25 minutes and let cookie bars cool before cutting into them.