Melt butter in a large frying pan. Add the diced onions and mushrooms to the pan and cook until the onions are soft and mushrooms have released their liquid, about 6-8 minutes.
Add minced garlic and cook until fragrant, about 1 minute.
Stir in 2 tablespoons flour and cook for a minute or two to cook out the raw flour taste.
In a small bowl combine chicken bouillon with chicken broth. Stir well.
Add the chicken broth mixture to the pan and heat until slightly thickened, stirring frequently. Be sure to scrap up the browned bits from the bottom of the pan.
Add garlic powder, onion powder, pepper and nutmeg to the pan.
In a small bowl combine ½ & ½ with a tablespoon flour.
Add the cream mixture to the pan and heat through, until soup has thickened. Do not boil soup once you add the cream. Stir frequently.
Taste and season with salt if needed.
Serve topped with a sprinkle of parmesan cheese and chopped fresh parsley if desired.