Preheat the oven to 180 degrees C
Peel and quarter the onions and place in a single layer in a 20cm diameter round pie dish.
If the onion are a bit large cut them into 6 pieces rather.
Melt the butter with the oil, brandy, vinegar and salt.
Stir in the chopped parsley and pour over the onions.
Roast the onions for 45 minutes and remove from the oven.
Increase the oven temp to 200 degrees C
Gently roll out the pastry on a floured surface until it is 1cm - 2cm larger than the pie dish and trim off the square edges.
Place over the onions once roasted, tuck in the edges of the pastry into the pie dish.
Sprinkle with the parmesan cheese and bake for 25 minutes until puffed up and golden.
Remove from the oven and leave to stand for 5 minutes before turning out onto a flat plate.
Crumble the chevin over the tart, sprinkle with some more chopped parsley and serve.
Adapted from Conrad Louw