In a heavy-bottomed pot, melt butter, add flour, and stir gently until blended; do not burn or let it darken. Add milk gradually, stirring all the while, then add half and half, stirring gently while blending. Add corn and green onions, and cook for a few minutes until tender.
Add crabmeat, pepper, salt, and soy sauce and simmer until very hot and small bubbles form around the edge; do not let boil. Adjust seasonings to taste. Garnish with sprinkles of chopped fresh parsley when serving and serve hot.
Variations: You may use 4 cobs of fresh corn instead of frozen or canned. Cut the kernels off the cob, scrape cob for juices, and then add to soup. Cook until corn is tender. Canned crabmeat or imitation crab may be used instead of fresh crabmeat. Use one 7 1/2-ounce can crabmeat (drained) and 8 ounces imitation crab (cut into small pieces). Combine the two and cook as noted above.