Add the beef to a large pot, season with salt and pepper, and brown
When the beef is browned, add your onion and garlic + a splash of beef broth to deglaze the pan, and cook for a few minutes until the onion has softened
Add the pumpkin, stir to combine, and cook for a minute or two, stirring often
Add your chili powder, cumin, both cans of tomatoes, and your beef stock. Season well with salt and pepper
Bring to a boil, reduce to a simmer, and cook for 30 minutes, stirring periodically
Stir in your cocoa powder and season to taste with salt and pepper!