1. Melt the butter in a saucepan.
2. Add flour and stir to mix the butter and the flour.
3. Add the milk little by little by stirring with a whisk until the flour starts to thicken.
4. Add white pepper and Castello® Double Cream Truffle.
5. Mix everything together with a ladle until you have a thick cheese sauce.
6. Cook the pasta al dente and drain the water.
7. Cut the champignons in slices and fry them golden in a little butter.
8. Mix champignons together with the cheese sauce and basil.
9. Pour over the tagliatelle.
10. Sprinkle a bit of fresh spring onion and serve.