Why was this butter so resistant to melting?

I made French Onion soup last weekend. The first step is to saute a boat load of onions in real butter.

Then I drain the butter off, and save it for later use on French bread and stuff.

I’ve gotten into it a few times in the last week, and noticed it was much harder than plain butter. It was difficult to get it out of the container I had it in.

Today I thawed out some fake crab, and decided to melt some of that butter to dip the crab it.

I nuked it for a minute. It’s been my experience that butter melts really fast, and starts popping after about 30 seconds…but this didn’t.

At the end of the minute I checked….and only about ¼th of it had melted.

I nuked it again for 30 seconds…barely any progress.

I ended up having to nuke it again for over a minute and a half to get enough to melt to dip crab it. It still wasn’t all melted, but enough was for my purpose.

Isn’t that odd? Do you know why?