I must admit that this is a bit of a draft as I'm completely working off memory. But, I'll take a bite at it ;-) and hopefully come back later with a more authoritative edit... (And of course, you should not be relying on this answer either way for Halacha).
Firstly, we have to figure out what type of Ikar V'tafel this is. [for a quick recap: the 3 types in short are 1) absolute 2) enhancers 3) mixtures]. I took a quick Google around and it seems like the cream is added after the cookie part is baked. This would therefore appear to not be a case of a mixture, which would make it the type of Ikar V'tafel that is "enhancers" (similar to a cracker with tuna).
However, I'm not 100% sure about this. Naturally, if this assumption is false, the entirety of this answer would fall off...
With that being said we have to figure out what's enhancing what. In other words, is the cookie enhancing the cream, cream enhancing the cookie, or neither? Believe it or not, this is generally subjective. In other words, we ask the person why he's eating it.
For example, I would say that for me the cream is enhancing the cookie. I really want to eat a cookie, but without the cream it would be pretty bland and dry. However, I could imagine that there are others out there (as you allude to in your question) that think otherwise.
Once that's determined, we get to the Halacha part. Because the cookie is Mezonos (and is used in a significant way) it gets a bracha either way. So:
- If the cream is enhancing the cookie, it's simply Mezonos.
- If the cookie is enhancing the cream, it would require 2 brachos.
- If neither is enhancing the other, it would also require 2 brachos.
All of the above applies to the case where the cookie is eaten as it is sold. However, if you were to go ahead and separate it, both components would require their own separate bracha. This is once again true due to the underlying assumption that this is a "enhancing" type Ikar V'tafel (if it would be a mixture, it would be a Machlokes if you separate it, IIRC)