Preheat oven to 200°C.
Toast caraway, coriander, and cumin in a dry pan until aromatic.
Grind toasted spices into a powder and mix with honey, lemon juice, and harissa.
Cut deep slashes into the lamb shoulder flesh.
Rub the lamb with oil and season with salt and black pepper.
Place garlic, onions, rosemary, and thyme in an oven dish and put the lamb on top.
Pipe the spice paste into the lamb slashes and seal the dish with foil.
Roast for 15 minutes at 200°C, then reduce to 160°C for 4 hours.
Rest the cooked lamb shoulder under foil for 20 minutes.
Soften chopped onions in butter without browning them.
Add garlic purée and cook until onions are translucent.
Tie bay leaves and thyme sprigs with string and add to the pan.
Add diced lamb belly and potatoes, seasoning with salt and white pepper.
Cover and cook on medium heat for 1 to 2 hours until juices release.
Add stock, boil, then simmer covered until potatoes break down.
Stir in chopped parsley, tarragon, and chives before serving with the lamb.