What i do in FitDay (i just use the free web version) is to skip forward to a 'new' day in my food log and add all the individual foods & such for my recipe or restaurant item. Then I create a new custom food and copy the total macro & micro-nutrient values. Now I have a unique custom food created (and only have to do it once). Then I just delete the values to clear out that 'day'

Granted its time-consuming, but you only have to do once, and for a free website, fitday is awesomely useful to me, so i dont mind.