Heat oil in a large pot over medium-high heat. Add onion, carrots, celery, thyme and tarragon and cook for 5 minutes. Season with bouillon powder, cayenne pepper (if desired), salt, pepper and paprika.
Add minced garlic and cook for an additional minute. Mix in flour and tomato paste and cook for two minutes.
Slowly stir in stock and crab meat then reduce heat to medium-low and let simmer for 30 minutes.
Stir in milk and Greek yogurt and cook, stirring continuously, until fully combined and heated through.