Put the oil and diced onion in a frying pan and gently warm on low heat for 10 minutes. You want your onions to soften up but remain white.
In the last minute add the garlic and mushrooms and stir in. After 1 minute remove from the heat and place to one side.
Preheat your oven to 180C/350F/Gas mark 4 and lightly grease a 2-pound loaf tin with a little olive oil.
Place your nuts in a food processor and pulse until they are roughly ground up, you don’t want them to get too fine. If doing it by hand place the nuts in a sealable plastic bag and bash them with a rolling pin.
Place the ground up nuts in a large mixing bowl with the grated cheddar and grated Parmesan and add in the chopped up parsley mix everything up.
Add your breadcrumbs to the mix and again mix in.
Scrape everything from your cooled frying pan including the oil into your mixing bowl and stir until everything is well combined. Add the lightly beaten egg and mix. Add at least a pinch of salt and pepper or more to taste.
Spoon the mixture into your loaf tin and press down hard onto it to get it to stick together.
Pop it into your preheated oven in the middle for 50 minutes. Once the time is up, check to see if it has a light golden colour on top if it does take it out and leave it in the tin for 5 minutes before turning out and serving.
Once cooled this nut roast can be kept in the fridge for three days and can be frozen for 1 month. Make sure it is fully defrosted before reheating it up in the oven or microwave.