- Bring a medium saucepan with filled water to a boil. Add fresh spinach and cook for 30 seconds. Remove spinach from the saucepan and drain on a paper towel-lined plate. Squeeze any excess water out of spinach. Finely chop spinach and set aside.
- Melt butter in a large Dutch oven over medium heat. Add onion, celery, bay leaf, and thyme and sauté for 5−7 minutes or until softened.
- Season the vegetables with 1 teaspoon of the salt and ½ teaspoon of the pepper. Add the garlic and sauté for 1 minute. Add the flour and stir constantly for 1−2 minutes. (Do not let the flour brown.)
- Whisk in the cream, oyster liquor, and reserved spinach and bring to a boil. Reduce heat and simmer for 20 minutes.
- Season with remaining 2 teaspoons salt and 1 teaspoon pepper. Add oysters and cook 5−8 minutes or until oysters are heated through and edges begin to curl.
- Remove soup from the heat and stir in Pernod. Serve immediately.