Preheat air fryer to 135°C/275°F (or 155°C/310°F for a conventional oven), if preheating is required.
Line a large bowl with foil to create a well. Then, line the foil with a sheet of baking paper.
Place the mushrooms, garlic, water chestnuts, rosemary and black pepper into the well. Drizzle in 1 tablespoon of extra virgin olive oil and mix well to coat.
Gently pull the corners of the foil up and towards the centre of the bowl. Twist thecorners together to make a sealed roasting pouch, but take care not to tear thefoil. It should look like a teardrop with a very thin, long top. (Note 6)
Place the roasting pouch into the air fryer and cook for 1 hour (or 1 hour and 15 minutes in a conventional oven). Once cooked, remove thepouch from the air fryer with a pair of tongs and put it back into the large bowl. Carefully open the pouch and let the mushroom mix cool slightly (about 10 minutes).
Add the mushroom mixture to a food processor (as well as any leftover drippings on the baking paper). Add the cottage cheese and remaining 1.5 tablespoons of extra virgin olive oil, and blitz until smooth. (Note 7)
Spoon the mixture into your serving bowl of choice, cover it with cling wrap, and set it in the fridge for at least 2 hoursto set. This is key to getting the firm texture of pate.
Serve with brown rice crackers or vegetables ticks. Enjoy!