We had a bunch of heavy cream leftover from making ice cream last week. In an inspired moment, I remembered this book that we have, 50 Science Things to Make and Do, and got Aidan to help me make butter. It's easy-peasy. All you have to do is pour some heavy cream into a jar, put the lid on tight, and shake! Our book says to shake it for 10-15 minutes. Aidan pooped out after five, and since I was in the middle of making the ice cream, the jar sat on the counter until I was finished and could work on it myself. I shook it for a minute or two before realizing there didn't seem to be much going on inside the jar. I peeked inside, and voila! The butter was ready. Yum!
Here's a photo of the book's cover. It has all kinds of fun science experiments for kids. I need to remember to break it out more often. If you'd like your own, you can find one on Amazon, or contact your favorite Usborne Books representative. I bought mine a few years ago, so I have no idea if it's even still in the catalog, but your rep should know!