In case you haven't noticed, "I Can't believe its not butter" isn't actually butter. Its made of mostly vegetable oil, a little buttermilk, water and salt. I think the vegetable oil will absorb your cannabinoids, but I don't know if this will resolidify well after cooking for several hours. I certainly would NOT try this myself.
If you want actual butter when you're done, I'd suggest starting with real butter (ie from a cow, not a laboratory).
Despite what you suggest above, real butter is about 80% milkfat, and will dissolve just about all the THC you care to throw at it.