That does look very delicious
I'm sure a flank steak is much nicer than the traditional London Broil you find here which is normally a top round or sirloin. I've found a big difference using "choice" meat instead of the less-expensive "select" grade. Most of the flank steaks I see in the market are smaller than the one you used.
There's also the question of broiling. The person I bought my home from broiled chicken constantly and one of the ovens was pretty dirty although they're both self-cleaning. I don't like wasting electricity running cleaning cycles which I've only done once in 12 years. I prefer to hand-clean the oven after I'm finished. I normally use the grill but then of course you can't do the mushroom/gravy step which really made your dish.
I know you don't worry about oven cleaning ever since you bought those rubber gloves and that pair of knee guards for faithful suisse chef Ralph.