Melt butter in a large soup pot over medium heat. Add carrots, celery, and shallot/onion, season with seasoned salt and pepper then saute until tender, 8-10 minutes — feel free to place a lid on the pot halfway through to speed up the softening process. Add the garlic then saute until fragrant, 1 minute.
Sprinkle in flour then stir and cook for 2 minutes. Slowly pour in chicken broth while stirring to avoid lumps. Add milk then turn heat up to high to bring soup to a simmer. Add cauliflower then turn heat down to medium-low and simmer until cauliflower is very tender, 10-12 minutes. Note: the cauliflower won't become "soft" but it should be very tender.
Scoop 2 cups cauliflower + a little broth into a blender then blend until very smooth. Be sure to crack the lid to let steam escape while blending. Pour blended soup back into the pot then add sweet corn and stir to combine.
Turn off the heat then add shredded cheese in two batches, stirring until completely smooth before adding the next batch. Taste then add more seasoned salt and/or pepper. Let soup sit and thicken for 10 minutes then serve.