You can, it will likely split but can be combined again. To freeze, cool the sauce to room temperature and then spoon into a freezer bag. To be safe from the sauce attracting odors, I recommend you also place the bag laying flat in a freezer container. If you are making a large batch and freezing several bags, it is best to find a container that will hold all of your Béchamel-filled bags. Just Lay them flat and stack them in your container. Label both the bag (or bags) and the cotnainer with the name and use-by date (freeze for up to 3 months), then place in your freezer. To defrost, remove a bag from the container and defrost in the fridge overnight. The sauce may look grainy after defrosting. Place in a saucepan over medium heat and reheat, whisking constanly, until fully heated and smooth. Stir in a teaspoon of butter to give it a fresh shine.