Cake was a good way to make an egg go a long way. One cooked egg was one thing for one person. One egg in a cake was a thing that would give the whole family something in their tummies.
My grandmother made the most amazing one egg cakes, a trick she learned during the war you wont be surprised to hear!
And YY to a slice of cake being a thing that kept you going, especially if money, and therefore food, was thin on the the ground so the only issue about portion sizes at dinner time was that they were too small. This was a time when a dinner was meat, spuds and two veg.
My GrandMIL had a wonderful story about when her then (now late) husbands boss invited himself for dinner during the war. They were in a protected profession and he was "well placed" so rationing was not something he ever dealt with. She served their steamed stodgy pudding as a first course. Boss thought this hilariously common. Until she offered him his dinner and he didnt want it as he was full, which was lucky as they only had enough for their family (and then barely), although they went without pudding so did go hungry that day. Boss never invited himself again but did make sure a few extras went GFIL's way.