My unopened unexpired container of organic whipping cream congealed at the top into something close to cheese but with a yellow cast and greasier feel is it butter?

* Whipping cream separates: When heavy cream sits for a long time, even in the refrigerator, the fat molecules can separate and clump together. This is especially common with organic cream, which may have less stabilizers.

* The yellow cast: The yellow color is likely from the fat separating and concentrating, making it more visible.

* Greasy feel: This is also typical of separated fat.

* Butter vs. separated cream: Butter is made by churning cream vigorously to separate the fat completely and form a solid mass. The congealed cream you're describing hasn't been churned, so it's not true butter.

What to do:

* Check the expiration date: If the cream is still within its expiration date, it's probably safe to use.

* Give it a good shake: Shake the container vigorously to mix the separated cream back in.

* Use it quickly: Once separated, cream doesn't last as long, so use it for cooking or baking soon.

If you're unsure about its safety, it's best to err on the side of caution and discard the cream.