1Pre-heat your frying pan on the hob. Swirl your oil in the pan.
2Add your chopped shallots, a pinch of salt, and some black pepper to the pan. Sweat the shallots for a couple of minutes, then add the green peppercorns.
3Add almost all of the sliced mushrooms, keeping a few back to add at the end. Continue to swear the ingredients down for a couple more minutes.
4Add both types of mustard to the pan, and mix together well. Continue to heat.
5Pour in a good glug of brandy, then use a long chef's match to flambé. Once the flame dies down, that's when the alcohol has burnt off.
6Pour in a splash of wine to the pan, and stir through.
7Reduce the heat of the pan to low, and stir in the creme fraiche thoroughly. Check the seasoning, and add more salt and pepper if necessary.
8Add the cubes of butter, a pinch of parsley, and the sliced mushrooms you kept back from earlier. Finally, splash in a little more white wine.
9Decant the sauce into a clean saucepan to serve at the table.