Prepare the Brisket: Season brisket chunks with salt and pepper. Heat olive oil in a large pot over medium-high heat. Add the brisket and cook until browned on all sides, about 8-10 minutes. Remove brisket from the pot and set aside.
Sauté the Vegetables: In the same pot, add the chopped onion and minced garlic. Sauté until the onions are translucent and soft, about 5 minutes.
Combine Ingredients: Return the brisket to the pot. Add the crushed tomatoes, kidney beans, chili powder, and beef stock. Stir well to combine all the ingredients.
Simmer the Chili: Bring the mixture to a boil, then reduce the heat to low. Cover and simmer for about 2-3 hours, stirring occasionally, until the brisket is tender and the chili has thickened. If the chili gets too thick, you can add more beef stock to reach your desired consistency.
Final Seasoning: Taste the chili and adjust the seasoning with more salt, pepper, or chili powder as needed.
Serve: Ladle the brisket chili into bowls and garnish with your choice of sour cream, shredded cheese, chopped green onions, or cilantro.