Heat the oil in a frying-pan and saute the onion rings (and green pepper blocks, if using) until very lightly cooked – make sure the onion rings remain intact. Drain them on absorbent paper.
Combine the apricot jam, vinegar, sugar, bay leaves, garlic, salt, pepper, turmeric
and curry powder in a ceramic or glass bowl and add the onion rings (and green pepper, if using).
Add the meat and fat to the mixture and marinate for 24 hours in the fridge, stirring 2 or 3 times.
If the apricots are not soft, soak them in a little water until plump. You might also want to soak the skewers so that the exposed ends do not burn to charcoal during the cooking process!
When you are ready to cook, thread the cubes of meat, apricots, mutton fat and onion rings onto the skewers. Pour the marinade into a saucepan, bring to the boil and keep warm to serve with the sosaties.
The sosaties should ideally be braaied (barbacued) over hot coals for about 10 minutes, turning frequently. Alternatively, you can grill them in the oven under a very hot grill, again turning frequently and basting as necessary.