Add ¼ pound mushrooms and saute until golden edges. Remove.
Add 1 Tablespoon butter, heat, then add ¼ pound mushrooms. Saute until golden and remove.
Continue cooking in batches until all mushrooms and butter are used.
Add cooked mushrooms and onions back to the hot pot. Stir in garlic, cook for 1 minutes.
Mix in flour, thyme, salt, and pepper then cook for 1 minute.
Turn heat off and slowly add 1 cup chicken broth, stirring continually to avoid any lumps. Continue to add remaining broth. Bring to a boil over medium high heat, then turn heat to low and simmer for about 15 minutes.
Add half and half to pot, and continue to heat until thickened to your desired consistency.