Roast pork hash

The last slices of roast pork from Saturday, but this time, we really made a hash of it. You can either hash by hand if you have the time and feel like meticulously chopping everything up in tiny little cubes, or use the robot-coupe, which is faster and more accommodating to those who are already hungry. Guess which method we use most often.
So: chop up two onions and salt, and start them frying in oil in a big, broad, oven-proof pan. While they're cooking, chop up a couple of big potatoes, peeled or not, as you choose. Add them to the pan, and shuffle them about to let them and the onions cook on all sides. Then add three or four cubes of frozen stock, preferably of the same type as the meat to be hashed, but others will do, or even water, ad lib. Cover the pan and let the potatoes steam and become tender. Chop up the pork, mince a handful of fresh parsley and sage leaves, and add all that last. Stir about to mix, pat down, and run under a hot broiler for four or five minutes, to get the top brown. Serve with HP or sauce Americaine, i.e. ketchup (which we used up the last of, in making BBQ sauce).