Combine potatoes, celery, onion and 4 cups chicken broth in a pan and bring to a boil. On medium high cook until potatoes are tender, 12-15 minutes. Strain and save liquid.
Put liquid back in pot and add half & half. Heat on medium. In a bowl combine melted butter and flour. Stir into half & half mixture. Once thickened add in the vegetables, the rest of the broth, bouillon, pepper and nutmeg.