Gently cook the onion and a pinch of salt in 10g butter for about 8 minutes, until translucent. Set aside to cool.
Cut into the pork fillet all the way up its length, so it can be opened up like a book. Season with salt and pepper. Combine the cooled onion with the breadcrumbs, oregano and prunes. Stuff this mixture into the pork, using kitchen string at regular intervals to hold the fillet in its original shape.
Put the pork in a freezer bag and add the wine, garlic and juniper berries. Marinate in the fridge for at least 1 hour, or up to 12, turning occasionally.
To make the cabbage, melt the butter in a large saucepan. Add the cabbage, apple and onions and cook gently for 10 minutes until softened, stirring occasionally. Add the remaining ingredients and continue to cook for 15 minutes or so, until soft with very little liquid in the pan. Season to taste and set aside. The flavour will improve if made the day before and reheated.
When ready to cook the pork. Preheat the oven to 190°C, 170°C fan, 375°F, gas 5.
Melt the remaining butter and the oil in a large frying pan. Drain the pork, reserving the marinade, and pat dry. Add to the pan and brown on all sides – about 6 minutes – then transfer to a roasting tin and cook in the oven for about 12 minutes.
Put the unwashed frying pan back on a high heat and strain the marinade in. Cook down for 5 minutes or so. Add the stock and cook down until syrupy, scraping at the base of the pan. Add the cream and bubble down for 2 minutes more.
Rest the pork for a few minutes before slicing and serving with the cabbage and the pan juices.
** Marinated, raw pork may be frozen for up to 3 months. Defrost in the fridge overnight before continuing with the recipe as below.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.