Heat oil in stock pot over medium high. Add onion and garlic and saute until golden, about 8 minutes.
Add broth, carrots, apple, ginger, curry powder, coriander, salt, pepper, and cayenne. Simmer, covered, about 30 minutes, or until carrots are very tender.
Puree soup with an immersion blender or in a food processor or blender.
Return soup to pot. Add milk and heat through but do not boil.