Here it is, with a few steps as well. Damn near too late.
Step 1: Sketch out the idea to see if it is more lame than I thought. Decide it's pretty lame, but I got nothing else. Well, I do, but don't have nearly the time needed. Press on.
Step 2: Start dropping in those vector shapes, leaving the pencil lines in a set as the top layer for a guide (40% opacity so they don't interfere much). All shapes built beneath the guide lines. Turn them off and on when needed.
Step 3: Move on to the cake. Get it close to the way I like it. Stop tracking what I'm doing. Go into text mode for the steps from this point on.
Steps 4-500: After I had the cake the way I liked it, I dropped in the orange background, made the word balloon and re-organized the type to fit better. Fiddled with the bottom text, dropped in my signature, moved on to the kid. Got his head mostly made when I realized that he is far too old/tall for the number of candles on the cake, so I doubled the number of candles on the cake by duplicating the set of existing candles, flipping it, rotating it and placing a grouped hue/saturation adjustment layer on the rearmost candles to make them a bit darker. Went back to the kid, finished his head, moved on to his body, added a chair, considered messing with it further, went "nah" and stopped.
There you go. Is that a tutorial or what?
Comments welcome, as always.