To the make the black pudding: Cook and drain the grains, chill. Cut the pork back fat into small cubes. Blanch and refresh in ice water and drain well. Sweat the onions in olive oil until translucent. Add the spices and cooked grains to the onions and continue to cook for 2-3 minutes. Add the back fat to the mixture and stir through the grains, season and cook for a few minutes. Blend the blood, pass through a fine sieve then add to the pan. Cook gently stirring constantly until the mixture thickens. Blast chill the mixture. When the mixture is cold, form into rolls using cling film and secure well at both ends ensuring it is an even shape. Steam at 88°C for 1 hour then blast chill.
Pulled pork: Score the skin of the pork butt and season well with salt and pepper. Place the pork into a gastro tray and cook on combi mode 87°C for 12 hours. While still hot remove all the skin and bones and any vascular membrane, then coarsely shred the meat. Blast chill. Form the cooled meat into rolls similar size to the black pudding compressing well and then blast chill.
Baja dressing: Combine all ingredients and season to taste.
Salsa verde: Sauté the onions and garlic in olive oil until translucent, add the spices and salt and cook gently for 2-3 minutes then blast chill. Combine the remaining ingredients with the onion mixture and blend using until smooth.
To assemble: Heat a cast iron skillet or individual paella pan. Heat olive oil and add the black pudding and pulled pork and fry until caramelized. Break up loosely. Add two eggs and then dress liberally with the prepared salsa verde. Bake until the eggs are just set. Dress the dish with baja dressing, nigella seeds, coriander cress and broken chicharrones. Serve in the pan.