Melt the butter in a small frying pan,
add the onion and cook on a medium
heat until soft and translucent, then
cool. Tip the pork into a large bowl and
add the onion, egg yolks and thyme.
Season well and mix together with your
hands – don’t overhandle or you will
make the burgers tough. Divide the
mixture into 4 and shape into burgers.
Chill for 30 mins to firm up.
Heat the barbecue and cook the
burgers for 10 mins each side. Top each
burger with a slice of cheese, followed
by 1 tbsp apple sauce, then return to the
barbecue and close the lid, cooking for
a further 5 mins to allow the cheese
to melt. If your barbecue doesn’t have
a lid, loosely cover with foil.
Quickly toast the buns, then serve with
the burgers and some salad leaves inside.