Heat olive oil in a large Dutch oven or heavy-bottomed pot over medium-high heat. Brown the ground beef for 5-7 minutes, breaking it into small pieces as it cooks until no pink remains and moisture has evaporated.
Add diced onion and minced garlic to the browned beef, stirring frequently for 2-3 minutes until aromatics become fragrant and the onion begins softening slightly.
Stir in chili powder, cumin, paprika, and oregano, toasting the spices for 1-2 minutes while stirring constantly to release their essential oils and deepen the cozy first cool night chili recipe's flavor profile.
Pour in both cans of diced tomatoes with their juice, tomato sauce, and beef broth, stirring well to combine everything thoroughly. Add salt, black pepper, and cayenne pepper according to your heat preference.
Reduce heat to low and add both drained kidney beans and black beans, stirring gently to incorporate. Simmer uncovered for 35-40 minutes, stirring occasionally, until the first cool night beef chili reaches your desired consistency and flavors meld beautifully.
Taste and adjust seasonings as needed—add more chili powder for deeper flavor or additional salt for seasoning balance. The longer you simmer, the more the warm comforting early fall flavors develop and intensify throughout the pot.