2) Add the onions and fennel with 1 tsp salt and 1/2 tsp pepper. Cook over low to medium-low heat for 15 minutes, stirring occasionally, until the onions and fennel are tender and lightly browned.
3) Add the garlic and thyme and cook for 1 more minute. Add the Pernod and cook for another minute, deglazing the pan. Cool slightly. Add the breadcrumbs and 1 tsp of salt to the stuffing mixture.
4) Lay the pork on a board fat side down, and sprinkle with salt and pepper. Spread the stuffing evenly on the pork and roll up lengthwise, ending with the fat on the top of the roll. Tie with kitchen string, rub with olive oil, and sprinkle liberally with salt and pepper.
5) Place the rolled pork loin on a baking rack on a sheet pan and roast for 30 minutes. Lower the heat to 180C/Gas mark 4 and roast for another 20 to 30 minutes, until the interior of the pork is 60C. (If the thermometer hits stuffing rather than pork, it will register a higher temperature, so test the meat in several places).
6) Remove from the oven and cover tightly with aluminium foil. Allow to rest for 15 minutes. Remove the strings, slice thickly, and serve.