Mine was making sourdough bread. I had no idea you could catch wild yeast in your house and use it to make amazing loaves of leavened bread with just flour, water, salt and captured yeast.

I haven't had store-bought bread for 6 months, and each loaf I wonder why I didn't know about this earlier! (Here's a good starter on making a starter! http://www.theclevercarrot.com/2014/01/sourdough-bread-a-beg...)