The problem with that dish is that I can't seem to find a good enough piece of salted pork (rimmat fläsk) in the UK. I've tried with regular bacon, but it's just not the same, I think mainly cause the slices of the salted pork to go with the potatos and onion gravy are thicker than regular bacon slices.
Once the salted pork has been pan fried, you fry up some chopped onions in the leftover fat from the pork to soften the onions up a bit, and then pour some regular flour on top and then add milk to make the sauce. Add further salt and pepper to taste.
Serve with boiled potatos.
Is preferrably eaten in the way of chopping the potatos down into small pieces and mixed up with the sauce to make kind of a creamy oniony potato mash.