Using a sharp knife, make incisions in the pork rind, 1cm apart, without cutting through the fat (or ask your butcher to do it for you). Pour boiling water over the skin, drain and pat dry with a cloth (paper towel will stick). Rub generously with salt and pepper and place the meat open on a shelf in the refrigerator while you prepare the filling; the cold air dehydrates the skin to ensure a crispier result.
Make the filling Heat the oil and fry the mushrooms until golden-brown and fragrant. Stir in the garlic and chilli and fry for another minute. Remove from the heat, season with salt and pepper and stir in the feta. Remove and allow to cool.
Preheat the oven to 160°C. Using a sharp knife, cut a horizontal slit in the thick part of the meat and place the filling inside (spread in an even layer with your fingers). Place the meat on a wire rack in a roasting pan, pour the beer, wine or stock on the bottom and roast for about 1 hour and 30 minutes. Turn on the oven grill and grill the meat until the rind has puffed up and is crispy; keep an eye on it, so it doesn’t burn. Turn off the oven and let the meat rest in a warm place (in the warming drawer or under a foil tent) for about 20 minutes before carving.
Make the rice Fry the onion in the oil in a pan until soft and glossy. Stir in the chilli, red pepper, harissa and rice and mix until all the grains of rice are coated with the fragrant oil.
Add the liquid, salt and tomatoes and bring to a boil; reduce the heat and simmer for 20 minutes or until all the liquid is absorbed and the rice is cooked but not mushy. Remove from the heat.
To serve Slice the avocado thinly and sprinkle with lemon juice, salt and pepper. Carve the meat and place the slices on top of the fragrant rice in individual bowls. Drizzle with the pan juices then top with the avo slices, fresh herbs and a sprinkling of extra lemon juice to taste.