IN a cooking class I was assisting with, some of the students let their heavy cream for a whipped cream go too long, and we ended up with butter - the instructor was pretty cool about it, just scooped it out, packed it in a crock and let it chill til we ate, and served it with some crusty bread! And privately gave the students what-for, for flirting when they should have been paying attention, lol!
It was just regular supermarket heavy cream - it whipped up very light in color and texture, and was very sweet; some of the students thought it would have been a little better salted.