Boil the 4 cups water, then pour it over the cashews. Soak them in the boiling water for 30 minutes.
Bring another large pot of water to a boil, then add the zucchini noodles and blanch quickly for 1-2 minutes. Remove the noodles with a slotted spoon and place in a colander. Immediately run cold water over them then turn them out onto a baking sheet lined with paper towels. Set off to the side until your sauce is done.
Add the asparagus to the same pot of water and cook for about 3 minutes until tender but still crisp. Drain the water and set the asparagus off to the side.
Sauté the prosciutto and mushrooms in the olive oil for 5 minutes over medium heat. Reduce heat to low while you make the sauce.
Drain the cashews, but reserve the soaking water. Blend the cashews with 1 cup of the soaking water in a blender. Add the lemon juice, nutmeg, basil, salt, pepper, and garlic and blend to a smooth sauce.
Add the sauce and the peas to the mushrooms and prosciutto and simmer for 7-10 minutes. Stir in the tomatoes and remove from heat. If your sauce is a little too thick, add a bit of the cashew water to help thin it out.
Serve the sauce over the zucchini noodles garnished with toasted pine nuts and fresh basil.