Use a sharp knife to make a small hole in the bag of mushrooms and cook in the microwave on full power (800W) for 2 minutes, or until defrosted. Boil the kettle. Pour 1 litre of boiling kettle water into a measuring jug and crumble in the stock cube, stirring until dissolved. Once the time’s up on the mushrooms, pour any liquid from the bag into the jug and give it a stir (this will give your stock depth of flavour). Place a large non-stick frying pan on a medium-high heat with 1 tablespoon of olive oil. Peel, finely slice and stir in the garlic for 2 minutes, or until lightly golden. Tip in the mushrooms, dried thyme and a pinch of sea salt and black pepper, and cook for 5 minutes, or until the mushrooms start to caramelise and any water has evaporated, stirring occasionally, then remove from the heat. Remove the contents of the pan to a board and finely chop half of the mushroom mixture, leaving the other half chunky and set aside. Peel the onions and finely chop with the celery. Return the pan to a medium-high heat with 1 tablespoon of oil. Stir in the onions and celery, then cover and cook for 5 minutes, or until softened. Tear off the leafy part of the parsley and set aside, then finely chop the stalks. Once the veg has softened, stir in the rice to toast for 2 minutes. Stir in the parsley stalks and finely chopped mushroom mix and cook for 1 minute, then pour in a ladle of stock and stir in a figure-of-eight motion until it’s all absorbed, popping the lid on every now and then for a couple of minutes to trap in the heat. Continue to add ladlefuls of stock until the rice is tender but still holding its shape – it should take around 15 minutes. Meanwhile, roughly chop the parsley leaves and pound them in a pestle and mortar with a pinch of salt and pepper until you have a bright green pulp. Muddle in 3 tablespoons of oil, then set aside. Remove the risotto from the heat, coarsely grate in most of the cheese (keeping a small handful aside for later), then stir in the reserved mushroom mixture. Cover the pan and leave to relax for 2 minutes until the risotto is creamy and oozy. Divide between plates, finely grate over the remaining cheese, drizzle over a little parsley oil and serve.