For the cream sauce, heat the oil in a large pan and fry the onions until soft and translucent. Add the stock and bring to the boil and cook until the volume of liquid has reduced by a third then puree this mixture until smooth. Return back to the pan and add the cream and cook over a low heat for another 6-8 minutes.
Preheat the oven to 220 C / 200 C fan.
For the meatballs, fry the onion in the butter until soft then transfer to a large bowl. Mix in the cream, milk, salt, allspice and breadcrumbs. Add the beef and pork mince and mix thoroughly by hand. Using an ice cream scoop that has been dipped into water, roll the mixture into balls, washing the ice cream scoop in between rolling each meatball. As they are rolled, place each meatball on a lightly oiled baking tray. Roast the meatballs for 10 minutes, or until firm.
To finish the meatballs, heat the oil and remaining 75 grams butter in a large frying pan and fry until browned. To serve, put the meatballs in a serving bowl and pour over the cream sauce. Scatter with a little chopped parsley and serve with mashed potato and ligonberry jam.