Took me four different tries, but before we left Madrid, I finally found a restaurant that served a typical Madrileño dish: callos, or stewed tripes. And yes, they were delicious. Unctuous and perfectly savory, just melt-in-your-mouth goodness. When cooking entrails, it requires some skill to get to this point. In the photo below, you can see a nice piece of crispy blood sausage in the center, too, which was the perfect counterpart to all of this goodness.
I think I may be drawn to tripes in particular in a quest for the ultimate Kosher sin: there is some evidence that this word shares an origin from the Yiddish word for food that is not Kosher – treif.