Add the last Tbsp olive oil to a soup pot and once it's warm add the onion, garlic, carrots,thyme and celery. Season with salt and pepper and cook over medium heat until onion is translucent and tender. Cube the butter and add it to the pot, once it melts sprinkle in the flour, stirring to combine, then lower the heat and simmer 2-3 minutes. Pour in the chicken stock and allow to thicken, turning the heat up to medium. Slowly add the milk, combining, lower the heat back down to low, and add the grated cheese and parsley.