Add the cocoa powder to melted butter or heat it with a splash of water or broth, then cook the cocoa for a minute before adding your can of chili to the pot.
the chili itself, add the cocoa straight into the chili. Just make sure to cook the chili for a few extra minutes to fully incorporate the cocoa flavor.
The amount you use will depend on how sensitive you are to bitter flavors because adding too much cocoa powder could overpower the chili, but just enough is a revelation.
Although cocoa might sound like a weird addition, it works well with stewed tomatoes and roasted chilies because of shared flavor molecules and important aromatic compounds.