Sauté the aromatics: Heat olive oil in a large pot or Dutch oven over medium-high heat. Add diced onions and cook for 4 minutes, stirring occasionally, until they become translucent and softened. Add minced garlic and cook for an additional 30 seconds, stirring constantly to prevent burning. You'll know it's ready when the garlic becomes fragrant.

Combine main ingredients: Pour in the chicken broth, then add the drained and rinsed great Northern beans, mild green chiles with their juices, diced chicken breasts, and corn kernels. The juices from the chiles add essential flavor depth, so don't drain them.

Season the chili: Stir in chili powder, ground cumin, dried oregano, salt, and black pepper. Mix everything thoroughly so the spices coat all the ingredients evenly throughout the pot.

Bring to a boil and simmer: Increase heat until the mixture reaches a rolling boil, then immediately reduce heat to low. Cover with a lid and let simmer gently for 10 minutes, or until the chicken is fully cooked through and tender. Resist lifting the lid repeatedly—trapped steam helps cook everything evenly.

Temper the sour cream: To prevent curdling and ensure silky texture, ladle about ½ cup of the hot chili into a small bowl containing the sour cream. Stir vigorously until the mixture is completely smooth and uniform in color.

Finish and serve: Pour the tempered sour cream mixture back into the pot, stirring constantly as you add it. Mix thoroughly for about 30 seconds to distribute the creaminess throughout. The broth should take on a beautiful, lightly opaque appearance. Taste and adjust seasoning if needed, then ladle into bowls and serve hot with your favorite toppings.