1. Bring a pot of salted water to a boil.
2. In the bowl of a blender, place the roughly chopped garlic, spinach sprouts, olive oil, and water.
Season with salt and pepper. Blend everything together, then season with a little more salt and pepper.
Add more water if necessary for a smoother pistou.
3. When the water is boiling, cook the spaghetti and quickly drain them.
Put them back in the pot and add the pistou. Mix well.
Stir for 2 minutes and cover to keep them warm.
4. Slice the onion and leek, then sauté them for 10 minutes until tender.
Slice the mushrooms and add them to the sauté pan, cooking for an additional 10 minutes.
Add everything to the spaghetti and mix well. Taste and adjust the seasoning if necessary.
5. Roughly crush the roasted cashews and sprinkle them over the spaghetti.