Take your mince and put it in a large mixing bowl, together with your onions, chillies, chilli flakes, pimento, salt and pepper, then give it a really good mix before adding your eggs and mixing again.
Take a decent handful of the mix (we made them about 150g) and shape it into a patty, then place it onto some greaseproof paper, you can layer these to make sure they don't stick together.
When the grill is good and hot (the coals are white or grey), place the patties onto the grill, add some wood to the fire and shut the lid for 5 minutes, make sure the vents are open. You can also place your rounds of onion on too.
Turn them over and give them another 5 minutes or so. You can flip them twice again to get some good crisscross griddle marks on them. You can check if they're done or not by using a probe, they should be between 130 and 135°F, which is about 55°C.
Let them rest whilst you cut up your buns and dress them with rocket, grilled onion, tomato and a nice dollop of BBQ sauce, then pop a patty (or 2) on each bun and tuck in.