Step 1 Melt butter in a large saucepan over medium heat. Saute onion and garlic until onion is tender. Whisk in flour, and cook 2 minutes. Stir in clam juice and chicken broth, and bring to a boil. Mix in corn, and season with salt, white pepper, thyme, and cayenne. Reduce heat, and simmer 15 minutes.
Step 2 Stir in cream, crab meat, and green onions. Heat through, but do not boil once the cream has been added.