You’ll need to brine the meat at least 24 hrs before your BBQ. First, spatchcock the chicken. Flip the chicken over so the backbone is facing you. Use a sturdy pair of kitchen or poultry scissors to cut down either side of the backbone, then discard. Turn the chicken over and push down firmly on the breastbone to flatten out the bird. Make a few slashes in each leg joint. (Watch a video showing how to spatchcock a chicken at bbcgoodfood.com/videos/spatchcock.)
Put each cut of meat in a separate, large sealable bag. Sprinkle 1 tbsp salt into each bag and massage it all over the meat. Squeeze the air from the bags, seal tightly and put in the fridge for 24 hrs.
Tip the remaining salt, fennel seeds and peppercorns into a mortar. Tear the bay into small pieces and add this too. Crush the ingredients with the pestle until finely ground. Add the cayenne, paprika, garlic salt and sugars, and mix well. Remove the meat from the bags and pat dry with kitchen paper. Cover each cut with the rub, making sure you get into every nook. Return to the fridge for at least 1-2 hrs while you prepare the barbecue, or up to 24 hrs.
You’ll need to start the barbecue 7-8 hrs before you want to eat. Heat the coals and leave them until ashen. Add your wood chips, if using. When the flames have died down and you’re left with smoky cinders, push the coals and wood chips to one side of the BBQ pit, then replace the grill and add the beef and pork, placing them above the empty side of the pit – this will ensure the meat smokes but doesn’t burn. Pull down the lid and cook the meat for 30-40 mins, turning every now and then, until a dark crust has formed around the meat. Don’t be afraid to take it quite far, the crust should be almost black (but caramelised as opposed to burnt). Heat oven to 140C/120C fan/gas 1.
Transfer the meat to roasting tins, wrap tightly with foil and cook in the oven for 5-6 hrs until really tender.
When the meat has 1 - 1 1/ 2 hrs to go, reheat the BBQ and wait for the coals to turn ashen before adding more wood chips. When the flames have died down, push to one side as before. Put the chicken on the BBQ, bone-side down, above the empty side of the pit. Cook for 20-25 mins on each side or until cooked through – check by piercing a leg to see if the juices are clear, or use a meat thermometer to check the internal temperature has reached 70C. Wrap tightly in foil and set aside to rest.
After 5-6 hrs, the beef and pork should be really tender. Remove from the oven and leave to rest for 15 mins. If you’ve made a BBQ sauce (see the Texas BBQ sauce recipe here), brush this over the meat for a glossy finish. Remove any string from the pork and shred the meat. Cut the chicken into portions and serve everything on a big platter with the sliced sweet onions, gherkins and sides.