I may have posted this before, a simple thing I like a lot. I found it a few years ago at the "Chocolate & Zucchini" blog.
It makes a dark brown "ink" that can be used on breads, like frosting is used on cakes. You can write "sourdough", "Peace on Earth", "Dad's favorite", whatever.
1 teaspoon cocoa
1 teaspoon flour
1/2 egg white
No cooking, use it to write on bread before baking.