Cook the pasta in a pan of lightly salted water according to pack instructions.
Meanwhile heat the butter in a large saucepan and cook the shallots and garlic for 2-3 minutes until softened. Add the mushrooms and cook gently for 10 minutes, stirring occasionally, until most of the liquid has been absorbed.
Stir in the Marsala Wine and cook until absorbed by the mushrooms, then stir in the Cream tarragon and spinach. Season well and cook until the spinach has wilted.
Drain the pasta and stir in the mushroom mixture. Serve immediately with grated cheese.

Variation:
Add 100g chopped pancetta and fry with the butter and shallots

(¹) The Président 3% fat is a reduced fat alternative to Crème fraîche.