Trim the mushrooms, slicing porcini mushrooms (if you can find some fresh) and tearing large delicate mushrooms, such as chantarelles or oyster mushrooms.
Heat the oil in a large, heavy-based frying pan over a low heat. Add the garlic and chilli and leave the flavours to infuse for 5 minutes. If the garlic begins to colour, simply remove the pan from the hob and leave to infuse in the heat of the pan.
Increase the heat to high, add the mushrooms and cook, stirring, for 3–4 minutes until the mushrooms are tender and golden. Remove from the heat and stir in the lemon juice, parsley and butter. Season with salt and pepper.
Cook the pasta in a large saucepan of salted boiling water until it is al dente: according to the packet instructions for dried pasta or for 2–3 minutes if using fresh pasta. Drain thoroughly, reserving a ladleful of the cooking water.
Return the pan with the mushroom mixture to a medium heat and stir in the pasta. Toss until well combined, then pour in the reserved pasta cooking water and continue stirring until the pasta is well coated. Serve immediately with Parmesan shavings.