This dish is based on umami, which is popularly referred to as savoriness. It is one of the five basic tastes together with sweet, sour, bitter, and salty. Marinade for at least 1 hour, but up to 24 hours. From NPR.
I got this easy, delicious recipe from a friend, whose friend used to serve this in her restaurant in Ireland (hence my name for the dish). The addition of fresh cilantro is key to the flavor of this dish in my opinion.