In a 2 litre saucepan, melt butter; stir in flour until smooth. Gradually stir in broth until smooth. Add salt, pepper and bay leaves. Simmer, uncovered, for 15 imuntes, stirring occasionally. Meanwhile, in another saucepan, saute the celery and onion in oil until tender. Add mushrooms; cook and stir until tender. Add to broth mixture; bring to a boil. Reduce heat; simmer, uncovered for 15 minutes, sitrring occasionally. Add cream; heat through. Discard bay leaves.