The work will take no longer (or very little longer) if you double the end product of your work.
If you have to cut up onions, cut up several and freeze the excess in small bags for use in later recipes. (I usually fill snack bags and put several snack bags into a larger bag to minimize the smell in the freezer. One snack bag is about one whole onion.) Most dishes taste better when you use fresh onion than if you use dried minced onion. Do the same thing with garlic -- both are good heart protectors.
If you are making meatloaf (or spaghetti sauce, or a cassarole), make two and freeze one for a later meal.
If you are browning ground beef with onions and/or garlic, double or triple the amount needed and freeze the excess for use in a later recipe. Making spaghetti sauce will be a snap when the beef and onion are already cooked.