Put a deep pan of water on to boil. As it boils, salt generously then lower in 150g of pappardelle and cook for 8 minutes.
Thinly slice 300g of chestnut mushrooms. Warm 6 tbsp of olive oil in a large frying pan, then add the mushrooms. Let them fry for 4 to 5 minutes until they start to toast, then add 2 very finely mashed cloves of garlic. Thinly slice 4 spring onions. Let the garlic and mushrooms cook for 1 minute or until the garlic is fragrant, then add the spring onions and continue cooking for another couple of minutes until soft. Stir in 3 tbsp of harissa paste.
Lightly drain the pappardelle, toss with the mushrooms and serve. Grate a little parmesan over at the table.