It's a story about a bear who lives alone and is trying to make his breakfast. A mouse keeps showing up in his house asking for a cup of tea. It's a cute story about a creature living alone, stuck in a rut who learns to enjoy the company of someone else and to share his space and time with someone.
Last school year I made a fairly simple bento lunch for my then 5 year old based on the book.
As you can see it really isn't anything fancy. I used a bear cookie cutter for the main sandwich and a mouse for the second. Using construction paper, a toothpick and a marker I made the sign from the book.
If you have young kids and don't know the book you should check it out at your local library or get yourself a copy on your favorite online retailer. It's a lot of fun to read.