Dressing mixture is made using several perishable ingredients and often includes raw eggs, meat or meat stock. This makes it perishable so it must be handled with care to avoid becoming sick.  When you follow the steps to properly freeze and then cook the dressing, it should be perfectly safe; however, you should always be careful never to leave perishable foods out of temperature controls for longer than 2 hours, label frozen foods with their prep dates, and always check your food for signs of spoilage before eating.