To make the stuffing, soften the chopped onion in half the butter. Melt in the rest of the butter, stir in the breadcrumbs and herbs and season.
Preheat the oven to Gas Mark 7, 220°C, fan 200°C. Remove the string from the pork. The skin will be scored, but add a few more slashes with a craft knife or very sharp kitchen knife in a diamond pattern.
Turn the pork over. If you are using leg, make a deep cut along the joint. Open it out, then press in the stuffing. Re-tie the pork into a tight cylinder. For loin, push the stuffing into the cavity.
Rub the joint with oil, then 1 tbsp sea salt flakes, pushing into the skin. Sit the pork on the sliced onion in a shallow roasting tin. Roast for 25 minutes or until the skin has started to blister and turn golden, then turn down to Gas Mark 5, 190°C, fan 170°C and cook for 1hour 15mins (or 50 minutes per kg/25 minutes per lb).
Half an hour before the end of cooking, cut the apples into chunky quarters, then toss in a ceramic baking dish with a squeeze of lemon juice. Cut the red onion into wedges then add to the dish with the oil, butter and seasoning. Roast on the shelf below the pork for 20 minutes or until tender. Stir in the sugar, herbs and another squeeze of lemon and roast for 5-10 more minutes, or until sticky.
When ready, transfer the pork to a serving board or platter (don’t cover). Spoon out the excess fat from the roasting tin, then set the tin over a gentle heat. Whisk the flour into the juices, cook for 1 minute, then slowly whisk in the cider until smooth, scraping in all the crusty bits. Add the stock, simmer for 10 minutes, then season to taste.
Spoon the sticky apples and onions around the pork, scatter with herbs if you like.
This recipe is the ultimate Sunday lunch treat. For perfect crackling, the fat and rind need to be as dry as possible. Pat with kitchen roll, then chill uncovered, skin side up, for 2 hours or overnight.
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For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home.