In a large pot, melt butter over medium heat. Add onion, carrots, and celery. Cook for 5 minutes until softened.
Stir in garlic and cook for 1 minute until fragrant.
Sprinkle flour over the vegetables and stir well to coat. Cook for 2 minutes to remove the raw flour taste.
Gradually pour in the stock while stirring to avoid lumps.
Add Old Bay, paprika, salt, and pepper. Bring to a simmer and cook for 10 minutes.
For a smoother texture, use an immersion blender to partially puree the soup.
Stir in heavy cream and crab meat. Simmer for 5 minutes (do not boil vigorously to avoid breaking the crab).
Add lemon juice and parsley. Adjust seasoning if needed.
Serve hot with crusty bread or oyster crackers.
