Preheat the oven to 400°F (200°C).
Peel, core and finely chop the apple. Mix with the lemon juice. Add in the cut-up prunes and the rosemary.
With a sharp knife, remove the tough outer skin of the pork belly, leaving the layer of fat intact. Resist all temptation to trim the fat off. This is the good stuff!
Now cut a large pocket into the thick of the pork belly. Be generous because now you need to stuff your 3 apples and your 20-odd prunes into this pocket.
Sew the opening tightly shut. (See note below)
Place the sealed fruit-stuffed pouch on a roasting pan. Make light incisions into the fat layer in a crisscross pattern, being careful not to pierce through to the meat. Salt and pepper.
Roast 1 hour in the oven.Reduce the temperature to 375°F (180°C), add a small glass of water to the roasting pan and roast an additional hour.
Spread the honey over the pork belly and roast 30 minutes longer.
Place the roasted pork belly onto a heated plate and cover with a tent of aluminum foil. Keep warm in the open oven.
Pour the Calvados and a little boiling water into the roasting pan and scrape thoroughly to recuperate all the good juices and other tasty crud that has encrusted itself onto the bottom of the roasting pan. Pour all this goodness into a saucepan. Add the sour cream. Let boil for 4-5 minutes.
Serve on top of, alongside and poured all over the hot pig belly.