Blend together butter and flour and stir into soup. Simmer gently, stirring until butter has melted and soup thickens slightly. Stir in cream, add salt if needed, and heat slowly until soup is steaming. Do not allow to boil. Pour into tureen and serve immediately.
Strip leaves and silk from corn and discard.
Put an ear of corn in a colander set over a bowl. With a sharp knife, carefully slice off tops of kernels, then scrape each ear to extract the pulp. Prepare each ear of corn in the same way. Measure the milk and add enough cream to make 1 cup. Combine with remaining ingredients.