Sauté diced onions, garlic, and jalapeños in a pot with oil until softened. Add diced chicken breast and cook until no longer pink. Stir in white beans, chicken broth, diced green chilies, cumin, oregano, and a pinch of cayenne pepper. Simmer for 20-25 minutes until flavors meld. Stir in sour cream and lime juice. Garnish with chopped cilantro, shredded cheese, and sliced avocado. Serve hot with tortilla chips or crusty bread. Enjoy your comforting white chicken chili!