That all looks good! Update away...
I feel like an ankheg is an odd but appropriate comparison for CR. The chocolate golem is probably not quite as good offensively and has much lower AC but has more hp to make up for it. Stick with the same CR 3?
That advancement will do nicely.
Tactics: Chocolate golems can follow only rudimentary instructions, attacking according to their creator's commands. Usually, they are ordered to spew their filling on heavily armored combatants in an attempt to blind those opponents and take them out of a fight.
How's that?
No one said these things have smart orders --- I mean, who would build a combat weapon from chocolate?
Very good, though!
Background: Chocolate golems are often created as guardians for young children... ?? Not sure there's much else to say here.
Hmmmm.
Background: Chocolate golems are a specialized form of guard employed mostly by the very wealthy. They often provide security at social gatherings, appearing merely to be extravagant desserts. In some cases, they are even ordered to allow guests to slice off small bites of chocolate.
Like all golems, the chocolate golem is a manufactured creature and has no place in nature. They are created only through magical means.
A wizard of at least 14th level must cast fabricate, geas, and limited wish following the construction of the chocolate figure and extensive preparatory rituals.
A priest of at least 11th level can create a chocolate golem through extensive ritual, preparation of the chocolate figure, and use of the following spells: purify food & drink, prayer, commune, and animate object.
*SNIP*
Anyone wishing to purchase a chocolate golem can expect to pay a minimum of 700 gp for a hollow golem, 1,000 gp for a solid golem, and 1,200 gp for a filled golem. The wizard’s labor costs and additional 2,000–3,000 gp.
That background sounds good to me.
The spells are a bit tricky, since there aren't really great lower-level equivalents for some of them, either. We could do something like lesser geas or prayer, bull's strength, and greater magic weapon perhaps, CL 7. How's that sound?