Preheat the oven to 400°F (200°C). Spread chunks of pumpkin on a baking sheet and roast for about 25 minutes until tender and slightly caramelized, then mash or blend until smooth.
In a large skillet over medium-high heat, buckle down and brown the ground beef until fully cooked, breaking it apart with a spoon for even cooking and a nice sear. Drain excess fat if necessary.
Add diced onions and minced garlic to the skillet with the beef. Sauté for 3-4 minutes until fragrant and the onions become translucent.
Transfer the cooked meat, onions, and garlic mixture to the slow cooker. Stir in the roasted pumpkin, kidney beans, diced tomatoes (with juices), chili powder, cumin, and cinnamon.
Pour in the chicken broth and give everything a good stir to combine the flavors evenly.
Cover the slow cooker with the lid and cook on low for 4 hours, allowing the flavors to meld and thicken, and the pumpkin to further soften into the chili.
Once ready, open the lid and gently stir the chili. Taste and adjust seasoning with salt and pepper as needed for balance.
Serve the pumpkin chili hot, garnished with your favorite toppings like chopped cilantro, shredded cheese, or sour cream if desired.
