Add the bacon to the large pot and cook over low heat, stirring occasionally, until the fat has been rendered, about 7 minutes. Add the onion, celery and bay leaves and cook until the vegetables soften, about 8 minutes. Add the flour and cook for 2 minutes, stirring constantly. Slowly stir in the milk until smooth, then stir in the cream. Add the reserved cooking liquid, stopping before you reach the grit on the bottom. Bring the chowder to a simmer over moderate heat, then reduce the heat to low and simmer for 15 minutes, stirring occasionally.