Blanch the tomatoes until skin comes loose, then skin, seed, and chop coarsely.
Saute onion in butter a few minutes, then add all ingredients except the milk and cream.
Simmer for about 25 minutes, and remove the cloves.
Transfer to a blender or food processor, and puree. Add half and half, and the milk. (If preparing before-hand, put aside in the refrigerator at this point.)
Heat up in a saucepan and sprinkle chives on top before serving.