Let me tell you something about cake.
Firstly, cake is not just carbon as many folks say. Cake is in fact, the combination of ash and hardened oils, said that you can now understand that cake will only form if you're patient enough to wait until the oils of the tobaccos harden, and if you know something about wood, you're aware that oils take at least a week to harden...
A quick way to do this:
1 smoke dry tobacco, until the bottom
2 spread the ash on the walls of the bowl evenly, you may want to compress the ashes against the bowl
3 wait a day or two for minimum harden
4 repeat the process
Final tip, let your pipe rest outdoors if possible, specially if you live in dryier areas with around 60% humidity
if not, dry it inside your home.
A good cake is a hard one. You may experience some problems with uneven spots after some time after the cake formation. If so, you don't need to worry, the normal smoking will fill up those spots again.
Almost anything highly in vanilla will burn into white ash, in other words, will burn completely. Stanwell sungold is a nice one.