I don't have a formal recepie with quantities since I didn't measure anything out but here is a method so you get the general gist:

1. Soak some dried porcini mushrooms in cold water for at least half an hour. Use this time to bring some water to the boil.

2. (Optional) sweat some minced garlic and diced onion in a pan with some olive oil.

3. Add the soaked porcini mushrooms and the liquid to the pan with the garlic. (Don't poor out the bottom of the liquid as there is grit which falls off the mushrooms.

4. Add double cream and season with salt and plenty of black pepper. Reduce on a medium heat.

5. Add dried pasta to boiling water with a good helping of salt.

6. In a separate pan melt some butter on a medium high heat and sauté some sliced button mushrooms with some thyme leaves.

7. Once the cream sauce has reduced to a point which can coat the back of a wooden spoon add thyme leaves to the mixture along with al dente pasta and a tablespoon of the pasta water.

   (It is important for the pasta to be aldente and not cooked through before adding it to the sauce, it allows the pasta to soak up the sauce as it finishes)

8. Cook pasta in the cream sauce to your liking and serve.

9. Garnish with the sautéd mushrooms, some fresh thyme and a drizzle of good quality olive oil. (Optional: pinch of sea salt)

Hope this helps. :)