Brown the ground beef and pork sausage in a large pot. Add onions and jalapeños and sauté until softened. Add garlic and cook for another minute. Add the fresh tomatoes, tomato sauce, chicken stock, kidney beans, black beans, bay leaves, cumin, salt, and pepper. Bring to a simmer and cook uncovered for 30–45 minutes, stirring occasionally, until the chili thickens and all those flavors come together. Remove the bay leaves, finish with butter, and adjust seasoning to taste. Serve over rice with sour cream and pickled jalapeños, alongside some toasted bread.
