Heat the oil in a medium-sized non-stick frying pan set over a medium heat. Once hot add the shallots and cook for about 5 minutes, stirring often, until starting to soften.
Add the garlic and cook for about 1 minute, stirring to ensure it doesn’t catch and burn. Add the mushrooms and cook for another 10-12 minutes, stirring often.
Meanwhile, bring a well salted saucepan of water to the boil, add the pasta and cook for 1 minute less than the packet instructions. Drain well, reserving the pasta water.
Add the spinach leaves to the mushrooms and cook for 2 minutes, stirring until wilted. Increase the heat and stir in the crème fraîche. Add 2 tbsp of the reserved pasta water and half the Parmesan. Mix well to form a smooth and creamy sauce.
Add the drained pasta and stir everything together - the pasta should be coated in the creamy, silky sauce. Add more pasta water and/or crème fraîche as needed.
Add the nutmeg and season to taste.
Spoon into bowls and sprinkle with the remaining Parmesan. Season generously with pepper and serve.