Begin by browning the ground beef in a lidded stockpot over medium heat. Allow to cook, breaking up with a wooden spoon, until completely cooked through.
Next, add the onion, celery, bell pepper, and jalapeno to the meat and continue cooking for 5-7 minutes until the veggies soften.
Once the veggies are soft, Add the garlic and cook for 1 minute.
Then, add the canned pumpkin, chili powder, cumin, smoked paprika, and coriander. Stir together until all spices are integrated into the chili.
Thin the chili with the water/stock and tomatoes and bring it to a low simmer. Add the kidney beans, salt, and pepper and cover, reducing the heat to low. Continue to cook for 1-2 hours, stirring occasionally, until the chili is deep in color and rich in flavor.
Skim off any fat off the top of the chili as needed. If the chili becomes too thick while cooking, add another ½-1 cup of water or stock.
When ready to serve, spoon some chili into a bowl. Top with pepitas, sour cream, and cheddar cheese.