Heat oil in a large heavy-based pot over medium-high heat. Add onions and sauté until transparent, then add the green peppers, jalapeños if using, and garlic; sautéing for another minute, until the garlic is fragrant.
Add the ground beef and cook until browned. Remove excess grease if necessary. Stir in the chili powder, cumin, brown sugar, oregano, garlic powder, salt, pepper, and paprika.
Add in the beef broth then the masa harina, quickly stirring to break up any chunks. Then add in the tomato paste, crushed tomatoes, kidney, and pinto beans.
Bring the liquid to a low boil. Then, reduce the heat (low to medium-low) to gently simmer the chili, uncovered, for 20-25 minutes, stirring occasionally.
Remove the pot from the heat. Let the chili rest for 5-10 minutes before serving.
Ladle into individual bowls, and top with your favorite toppings.