Heat the olive oil over medium-high heat in a large stock pot or Dutch oven. Add the butter and let it melt. Add the onion, salt, and black pepper and cook, stirring occasionally, until translucent and starting to brown. Add the garlic and quinoa and cook, stirring, for 30 seconds. Add the corn and let cook for another 3-4 minutes.

Add the broth, cream, potatoes, oyster liquid, and cayenne pepper and stir. Bring to a boil, reduce heat, and let simmer, uncovered, for 30 minutes or until the potatoes are tender. Add the oysters and let simmer just until they start to curl, about 5 minutes. Stir in the green onions and serve, garnished with parsley and chili oil, if desired.