In a dutch oven or heavy skillet on medium heat, melt the butter and the olive oil. Add the celery, onion, carrots and thyme. Saute until vegetable are medium tender. Add the flour. Cook this while stirring for atleast 3 minutes to take the raw taste out of the flour. It will become thick, just keep stirring. Add the chicken broth slowly. Keep adding as much broth as you like for the stew thickness you prefer. Simmer.
