It's a Swedish version of the meatballs, and its typically served in a beef based mushroom and cream sauce on top of mash potatoes. It's a very homey and very comforting dish, and a nice alternative to the Italian meatballs in tomato sauce.
First and before you get the meat out of the fridge, get everything ready (you don't want ground meat out of the fridge for longer than necessary).
Start with the onion. Chop it very finely, season it lightly with salt, and gently cook it on low heat in a non stick skillet with a Tbsp of oil and 1/2 a Tbsp of butter until just golden. (Don't let it burn, it will turn bitter !) Let it cool, and reserve.
Make the breadcrumbs, and soak them in 1/4 of a cup of cream. Start adding the cream slowly, you don't want it dripping wet, just soaked, and the quantity of cream to add might depend on how moist your bread already is. Reserve.
Beat and season the egg, reserve.
Once this is done, get the ground meats out of the fridge and combine them (beef and pork) with the soaked bread, the beaten egg, the cooked and cooled onion, the nutmeg, and the allspice. Incorporate everything well, and salt and pepper to taste. Then cover and put back in the fridge for about half an hour. Don't overmix or the meatballs will be tough.
After half an hour, take your meat mixture out of the fridge and start to shape your meatballs (I make mine bite size, they cook faster and its easier to eat), and fry them until golden brown in a cast iron casserole (cast iron because it keeps the heat very well) in the rest of the canola oil with 2 Tbsp of butter for the taste. Once golden brown on all sides, Put them on paper towels in a tray and reserve.
In the same cast iron casserole, throw out most of the fat, and then saute the mushrooms on medium heat in what's left. Squeeze in the juice of half a lemon, and a few dashes of Worcestershire sauce. Once the mushrooms are cooked, deglaze the skillet with 1 cup of beef stock and scrape all the brown bits from the bottom of the casserole. Be careful with the salt at this stage, because the beef broth is already salted. You can always adjust the salt later.
Turn the heat to low and then slowly add the can of Campbell's mushroom soup, and the heavy cream (1 cup).
Once the mushroom sauce is nice and bubbly, add the meatballs back in, and let reduce on low for 30 to 40 minutes, until the sauce has reduced a third to a half (depending on how thick you want the sauce to be), and the meatballs are cooked through and the flavors have all combined.
Adjust salt and pepper to taste.
Serve on top of fresh mash potatoes, or buttered noodles.
I have added pictures of several stages of the dish to help you out.
NOTE : leftovers freeze beautifully. It's also a great dish to prepare a day ahead of time, because its even better reheated the next day. Just make sure you don't reduce the sauce too much when you cook it if you know you are going to serve it the next day, the sauce will finish to reduce as you reheat it (on low).