I joined three rambunctious dogs on a truffle hunt in the dense forests of the Istria Peninsula during my recent visit to Croatia. I love the intense, earthy flavor of truffles, a rare type of edible fungi that flourish symbiotically amid the roots of oak and other trees.   But I knew little about truffles and I had never been on a truffle hunt. During my truffle-hunting tour, we discovered several black truffles. I learned about the history of truffles and how to cook with...