Freezing food stops the growth of bacteria ... Freeze them in silicone muffin cups or in ice-cube portions to make it easy to use what you need. Keep a bag in the freezer for parsley stalks ...
First, make enough roux for the amount of gravy you’ll be serving (or make a bigger batch if you’ll be using it for other soups and sauces; it’s easy enough to break apart after freezing).