Core each onion. I prefer the method of using a sharp paring knife as a 'drill', poke into the centre and twisting. Repeat from the other cut side, then push with your thumb; the centre should pop out.Then use your fingers to work around the remaining onion until you leave a shell just 2-3 onion layers deep.
Coarsely chop a third of the removed onion and discard the rest. (Don't throw it away, though, freeze it for stocks, stews or soups).
Mix the chopped onion with the minced beef.
Dice the chilli pepper as finely as you can and add it to the beef.
Throw in the Worcestershire sauce, thyme, fennel seeds, salt and pepper, then mix well.
Stuff the onions with the minced beef mixture.
Wrap each onion with 2 strips of streaky bacon.
Take half of the BBQ sauce and brush it over the bacon-wrapped onions.
To Cook on a BBQ:
Add the onions to a hot grill and cook for an hour in an indirect heat 'zone' at around 160°C-170°C or 320°F-340°F.
Brush with the remaining BBQ sauce and move to the direct heat section of the BBQ for a final 5 minutes.
To Cook in an Oven:
Place the onions on a baking tray and place in a preheated oven at 170°C or 340°F and cook for an hour.
Remove the onions from the oven and then turn it up as hot as it will go, flip it to fan mode if you have that option.
Brush the onions with the remaining BBQ sauce and cook for a final 7-10 minutes or until nicely coloured.