Place chicken livers in a large bowl, and pour in 3 tablespoons olive oil, vinegar, and lemon juice; season with garlic, cumin, coriander, chili flakes, bay leaves, salt, and pepper. Stir together, and refrigerate for 1 to 2 hours.
Remove livers to a bowl, and reserve marinade.
Heat 1 tablespoon olive oil and butter in a large skillet over medium heat. Stir in onion, and cook until tender, about 7 minutes. Increase heat to medium-high, and stir in chicken livers; cook for 2 minutes, being careful not to overcook the livers. Stir in the tomato paste, Worcestershire sauce, chicken stock, and the reserved marinade. Simmer gently for 5 minutes. Pour in brandy, and heat through.
