Soak the dried mushrooms in enough boiling water to cover them and set aside.
Cook spaghetti according to packet instructions.
Saute the portobello mushrooms in the rapeseed oil and garlic until browned and juicy. Season with black pepper while they are cooking.
Drain and rinse the re-hydrated mushrooms.
Add to a blender along with half the mushrooms, the soya yoghurt and a few basil leaves. Whizz until smooth. If the sauce is too thick, thin with a little soy milk or other dairy free milk.
Drain the pasta and coat in the sauce,
Serve the pasta immediately and top with the remaining mushrooms and herbs.