Selat Solo also known as Racikan Selat or Kentang Bistik oddly enough originates from the city of Solo in Central Java and obviously is Western influenced. In one of my late father's satirical stories titled "Wong Solo" or the People of Solo, he indicates that both rival palaces back in the day prioritized on good food and thus brought European cooks over to teach the courtiers how to cook Western food. So I suspect though cannot confirm that this is how this dish came about.
The beef is basically like a thick stew but instead of cutting it up in small pieces, it is sliced in fairly significant pieces. It is also sweeter and peppery - the sweetness coming from sweet soya sauce. And this is balanced with a mustard sauce that is similar to Hollandaise sauce and is made from; hard boiled egg yolks, garlic, salt, pepper, white vinegar and mustard of course. The result should give you a multitude of sensations in your mouth; sweet, savory, peppery with a hint of sour.
It has been over 15 years that I haven't made this and I learned it by observing my mother cook it during special occasions. Unfortunately the times I ate this whether in Solo or in Jakarta, it was always disappointing and never even came close to how I knew it to be. I woke up super early this morning thinking this dish, why hadn't it been on my menu for all these years, because it's actually very simple to make. So I began to prepare making it and by noon, I had it for lunch. Sometimes cravings cannot be helped - you just have to succumb to it, and when you do...it feels so good!