This is how we, I mean me, eat cake at the house. Get a fork. Draw a line in the icing of the piece of cake you intend to eat. Eat to your line. Notice that the line is uneven and will look like you ate from the pan. Work hard at evening it up.
Think that you need just a little more and draw a bigger line. Forget all propriety. Just leave the fork in the pan. No sense in dirtying up more forks. It will be there for later.
Who says you can't have your cake and eat it, too?