Open and drain clams, reserving both clams and broth.

Heat butter in a soup pot. Add the onion and potato, and cook until the onion is soft. Add the reserved clam broth, and simmer until potato is tender.

Add the milk, half and half, and thyme. Bring to a low simmer, stirring regularly.

Add the roux cubes, and stir until slightly thickened.

Add the corn, and heat. Add the reserved clams, and just heat to serving temperature, being sure to avoid bringing it to a boil.