Place your choice of mushrooms in bowl of hot water to rehydrate.  Follow the packet instructions but work on 30 minutes for this part of the recipe.  Rinse your mushrooms. Combine the nuts, sliced button mushrooms and Shitake or Porcini, the parsely and the garlic in a food processor and pulse till coarsely chopped.  (I don't have one, but used a liquidiser quite effectively.  You may just have to stop and toss the contents around between the pulses - the handle of a wooden spoon does great for this!).  With the machine running add your half cup of olive oil and process till all the ingredients are finely chopped. 
I must mention that most freshly homemade pesto's oxidise quite quickly.  To avoid this always place a piece of plastic wrap directly onto the surface of the finished product and refrigerate. Alternatively add a thin layer of olive oil over the surface of  your pesto.  If your pesto has discoloured a quick toss around brings it back to it's original glory!....now get the pasta into a pot.........pesto it, and enjoy!