Begin by chopping all the vegetables. If using raw chicken, cut into bite size pieces.
In large pot, melt butter and add vegetables, garlic, and raw chicken (if using). Cook and stir over high heat 3-5 minutes, until onion starts to soften and chicken starts to look white, but vegetables are not starting to brown.
Pour in the broth. Stir in poultry seasoning and black pepper and bring to a gentle boil.
The soup should boil 20-25 minutes total. If you are using country style egg noodles that take 20 minute to cook, add them after soup simmers for about 5 minutes. If you are using traditional egg noodles that take 10 minutes to cook, allow soup to simmer for 15 minutes before adding noodles.
When noodles have softened, reduce heat to medium and stir in cream cheese. If using precooked chicken, add it now. Cook and stir 2-3 minutes until cream cheese is completely melted and incorporated. It can be helpful to use a whisk.
Serve immediately. Refrigerate leftovers. You may want to add additional broth when rewarming leftovers, as the noodles will absorb liquid as the soup sits.