Heat a dry skillet over medium-high heat. Toast the guajillo chiles for 1-2 minutes until toasted and fragrant, flipping them every 30 seconds so they don’t burn. Transfer to a bowl and allow to cool for 5 minutes.
Blend the toasted chiles in batches in a spice grinder or small blender until it's a fine powder. Transfer the chili powder to a bowl.
Add the garlic powder, oregano, cumin, coriander, cocoa powder, and ground cinnamon into the chili powder bowl and mix together until fully combined.
Use immediately or store in an airtight container at room temperature.
Notes
Remove the seeds. Make sure to remove all the seeds from the dried chilies to keep it at a mild heat. Once the seeds are ground into a powder it's hard to mellow out the heat.
Use the right cocoa powder. Dutch-processed cocoa powder has an earthy and darker flavor compared to natural cocoa powder, which in general is more sweet. I don’t recommend substituting natural cocoa powder, so this ingredient can be left out if you don’t have it.
Batch it. This chili powder recipe can last up to 6 months at room temperature when sealed, and up to a year if refrigerated, making it great for batching.
Cool the toasted peppers completely before grinding them. They crisp up as they cool, making it easier to grind into a powder.