Onions and celery finely. Peel the potatoes and cut into cubes, ham also cut into cubes. The butter is melted in a saucepan. Add onion and celery. Fry on low heat for 4 minutes, stirring occasionally. Add all other ingredients in succession, with the exception of maize (milk from a can), and the ham. Is reduced to the minimum temperature and allowed to simmer for about 15 minutes. Then the fire increases, add the two types of corn and sliced ​​ham. Stir the soup, add salt and put pepper. Allow to stand for a few minutes, stirring often. Then served hot, accompanied by toasted baguette.