The first time I had doganitang (도가니탕), or Korean ox knee soup, I had just finished an English lesson and my 70 year old student invited me to lunch. He was the kind of older Korean guy there was no declining, so I went along and was quite taken aback when the soup he’d ordered us was filled with some sort of gelatinous meat. I wasn’t completely sold at first. But my old friend had good taste, and I knew to trust him and eat what was in front of us. Over the years, doganitang has become one of my favorite Korean soups. On a scale of basic to adventurous…