Bring the water to a boil and add 1/2 teaspoon of salt. Sprinkle the cornmeal slowly into the water, stirring continually to prevent clumping. Lower the heat, cover with a lid and cook for about 40 - 45 minutes, stirring from time to time.
Add the butter and the Parmesan cheese and stir. Pour the polenta onto a cookie sheet until the polenta is about 1/2 inch (1 cm) thick.
Smooth evenly and let cool until firm. For the soup, peel the onion and the garlic, cut in half, then finely chop. Fry the onion and the garlic in butter. Drain the corn kernels and sauté 2/3 of the corn with the onions and garlic. Pour in the milk, bring to a boil, then puree and strain through a fine-mesh sieve. Season the soup with salt and pepper.
Add the processed cheese and cream and simmer for about 10 minutes, stiring occasionally. Place the tomatoes in hot water for a few seconds, then into cold water and peel. Cut the tomatoes into quarters, de-seed and chop. Wash the parsley, shake dry, then finely chop. Cut the polenta into cubes.
Toast the polenta in a skillet until lightly browned. Fry the chopped tomatoes together with the remaining corn kernels in butter until warm. Stir in the chopped parsley.
Break the salmon into pieces and season with pepper. Pour the soup into 4 bowls. Add a few spoonfuls of the tomato - corn mix, followed by some diced polenta. Serve hot. Serve the remaining polenta cubes on the side.