In a large pot of salted boiling water, cook the pasta until al dente. Keep ½ cup (125 ml) of the cooking water. Drain the pasta and lightly oil. Set aside.
In the same pot, soften the shallot and garlic in the butter. Sprinkle with the flour and cook for 1 minute, stirring constantly. Add the white wine and bring to a boil, stirring with a whisk. Add the cream and bring to boil.
Stir in the spinach, cheese and herbs. Return the pasta to the pot and toss to coat with the sauce. Reheat and add the reserved cooking water or more cream, as needed. Adjust the seasoning. Garnish with pieces of steamed salmon confit and arugula, if desired.