Brown the beef in a large Dutch oven over medium-high heat, breaking it apart with a wooden spoon until no pink remains, about 7-8 minutes. Drain excess fat, leaving about 1 tablespoon in the pot for flavor. Transfer meat to a plate and set aside.
Heat olive oil in the same pot over medium heat. Add diced onion and bell pepper, cooking until softened, about 5 minutes. Add minced garlic and cook until fragrant, about 30 seconds more.
Return beef to the pot and add all the spices: chili powder, cumin, oregano, smoked paprika, cinnamon, and cloves. Stir continuously for 1-2 minutes to toast the spices and enhance their flavors.
Add the pumpkin cubes and stir to coat with the spice mixture. Cook for 3-4 minutes, allowing the pumpkin to slightly brown and develop flavor.
Pour in the crushed tomatoes, diced tomatoes, both types of beans, beef broth, maple syrup (if using), and cocoa powder. Stir well to combine all ingredients thoroughly.
Bring the mixture to a boil, then reduce heat to low. Cover and simmer for 45 minutes, stirring occasionally to prevent sticking.
Remove the lid and continue simmering for an additional 15 minutes to thicken the chili to your desired consistency. The pumpkin should be tender but still hold its shape.
Taste and adjust seasoning with salt, pepper, or additional spices as needed. Remember that flavors will continue to develop as the chili sits.
Serve hot in bowls with your choice of toppings. A dollop of sour cream helps balance the heat, while cheese adds richness.