Heat the oil in a soup pot over medium heat. Add the onion and garlic and cook 5 minutes. Add the flour and stir to combine. Slowly, stirring constantly, pour in the stock. Mix in remaining ingredients, except chopped parsley, and simmer 20 minutes. Puree mixture, in batches if necessary, until smooth. Return to the pot and bring back to a simmer. Stir in chopped parsley, adjust seasoning, and serve.