Pre-heat the oven to 200° C.
Rub the pork fillet with the groundnut oil, then season with the ground cumin, salt and pepper. Place on a roasting tray and roast for 40 minutes.
Meanwhile, whisk together the gravy granules with the boiling water in a small saucepan. Simmer and whisk over a medium heat until you have a smooth gravy. Remove from the heat and keep to one side.
Remove the pork when it is cooked and cover loosely with aluminium foil. Let it rest for 5 minutes. Meanwhile, reheat the sauce and add the pearl onions to it. Warm them through for 5 minutes. Thinly slice the pork after it has rested for 5 minutes. Spread the slices out in a fan on serving plates.
Garnish with the grape halves and the onions in the gravy. Pour a little more gravy over the grapes and onions then sprinkle them with the cumin seeds. Garnish with sprigs of parsley leaves before serving.