1 Preheat the oven to 200°C. Heat a third of the butter and olive oil on medium in a large sauté pan (frying pans and woks work just fine too!) and half the mushrooms with a sprinkle of salt, pepper and a third of the thyme leaves. Cook for about five minutes, take out and then repeat with the other half of mushrooms.
2 Slice the onions and crush the garlic while the mushrooms are cooking away. Once they have cooked, set to one side, add the remaining butter and olive oil and cook the onions until softened but not browned.
3 Add in the crushed garlic and cook for a couple of minutes until fragrant and everything smells delicious. Do not let it burn or it will get bitter. Add in the white wine (or veg stock if you prefer) to deglaze the pan, making sure to scrape up any delicious brown bits that have formed on the bottom. These will help make your sauce extra tasty, so you want all these!
4 Add in the cooked mushrooms and half the amount of blue cheese you are using. Stir it all up and continue to cook on medium until the sauce has thickened and you want to eat it out of the pan.
5 Meanwhile, beat your egg for the egg wash and place the puff pastry on a grease-proof lined baking sheet.
6 One the sauce has thickened up, pile up the mushroom mix in the middle of the puff pastry square, leaving a good lip all way round. Fold the edge of the puff pastry all way round, overlapping and pinching to seal. This is supposed to look rustic so don’t worry about it winning any beauty prizes! Add the remaining blue cheese and thyme sprigs to the top and give a good brush with the egg wash.
7 Sprinkle the pastry with a bit of fresh black pepper and pop in the oven for 25-30 mins or until the pastry is beautifully golden. Let it sit for 5 minutes while you get a quick salad ready and get out your dinnerware, serve at the table for extra brownie points and enjoy.