Start by having your mise-en-place in place as this is a bit of a quick process.
Melt your butter in a large soup pot. Once melted, add in the celery, onion, and carrots, and cook until the onions have fully sweated, roughly 7 minutes. Next gently stir in the flour, and continue to stir until it just gets slightly browned, about 3 minutes. Now add in the thyme, and bay leaf.
Next, add in the milk, and the chicken stock, and continue to stir until the flour smooths out and creates a thickened sauce. Season with salt and pepper, then add in the chicken and potatoes.
Next add in the corn, and cook for about 15 minutes, stirring often. Taste and adjust any seasoning, if necessary.
Now you are ready to serve.
Get a soup bowl ready, ladle in the chicken and potato chowder, and spring some cheddar cheese onto the top of the chowder.