Add ~1.5 tbsp olive oil to a large pot over medium-high heat. Once hot, add the mushrooms and fry until they build up a golden crust. Try and keep them spread out as best you can (helps them caramelise & prevents them steaming). Season with good pinch of salt & pepper towards the end then remove.
Top up with oil if needed, then add the sausage. Break it up with your wooden spoon (I like small chunks) & fry until it builds up a nice golden crust (important to develop flavour). Add garlic & fry for another 30secs or so, then pour in the wine. Rapidly simmer for a couple of mins until it almost completely evaporates & the smell of alcohol disappears, using your wooden spoon to deglaze the pan.
Pour in stock then stir in cream, pasta & mushrooms. Bring to a simmer, reduce the heat slightly and cook until the sauce reduces & thickens and the pasta is al dente. If the sauce dries up before the pasta cooks, just add in a splash of hot water or stock.
Turn off heat & stir in parmesan & parsley, then stir in spinach until it begins to wilt. Check for seasoning and adjust with salt & pepper (season well to bring out the best in this simple sauce), then serve up with more parmesan & parsley if desired.
