I haven't tried this yet, but it is from Devin Alexander. She says: It's easy to throw together a Big Mac?like burger in minutes once you have the sauce made. So to save time, make a big batch of the sauce, omitting the onions (they are the only ingredient that will spoil quickly). Refrigerate the sauce in a plastic container for up to 1 month. When you're ready to enjoy a burger, simply add the correct quantity of onion to the amount of sauce you're using.