1 Heat the olive oil and butter in a large frying pan or wok until gently foaming.
2 Add the mushrooms and garlic, then turn the heat to high for a couple of minutes to cook the mushrooms. Add the parsley, season generously, then remove from the heat.
3 Cook the spaghetti as per packet instructions in a pot of salted water.
4 Meanwhile add most of the Parmesan into the eggs and mix.
5 When the spaghetti is ready, lift it out with tongs or a pasta fork and add to the mushrooms, quickly followed by the egg and Parmesan mixture.
6 Stir the spaghetti so the egg mixes and thickens but doesn't scramble, and mix the mushrooms through.
7 Season and add a few tablespoons of pasta water, so the mixture is moist but not wet. Serve immediately with the remaining Parmesan sprinkled on top.