First prepare the stuffing:
Cook the onion and garlic in butter until soft, then add the herbs and breadcrumbs. Cool a little before mixing in the egg and seasoning well with salt and freshly ground pepper.
Preheat the oven: Gas Mark 2,150°C (300°F).
To prepare the meat:
Trim off any excess fat and prick the centre of the meat with a kitchen fork, then combine all the Spicy Paste ingredients together and brush the meat with this mixture. Spread the stuffing over the meat, then roll it up and tie firmly with cotton string.
Brown the meat with a little oil in a hot roasting tin and cook in the preheated oven, seam side up - preferably on a rack over the tin - for three hours. Halfway through cooking, remove the joint from the oven and brush liberally with the Spicy Paste; return to the oven seam side down and continue cooking.
To make the sauce:
Bring everything to the boil and simmer for 15 minutes, then discard the thyme, liquidise the mixture, strain and season to taste. If it seems too thick, adjust the texture with extra stock. Serve the sliced meat on heated plates with its sauce.