Heat the sunflower oil in a large, heavy-based saucepan to 180°C.
Stuff the peppers with the chopped mushrooms, then drizzle with the olive oil and season well.
Whisk together the flour and chilled water with seasoning in a mixing bowl until just combined (it's okay if there are lumps of flour in the batter). Dip the peppers in the batter then deep-fry two at a time for 4-5 minutes until the batter is crispy and the pepper is cooked.
Repeat with the remaining peppers, and serve in a terracotta serving bowl with sprigs of parsley as a garnish.
*This recipe is very indulgent so shouldn't be eaten too often. But it's perfect for those special occasions!