Bring a large saucepan of salted water to a boil. Add the spaghetti and cook until al dente.
Before draining, reserve 150ml of pasta water for the sauce.
Combine the spinach, pistachios, silken tofu, nutritional yeast, garlic, lemon juice, salt and pepper in a jug blender.
Slowly add the olive oil and then 120ml of the reserved pasta water while blending, until the sauce becomes creamy and smooth.
In a large mixing bowl, combine the cooked spaghetti with the spinach-pistachio sauce.
Stir well to coat evenly, adding more pasta water if needed to thin the sauce.
Garnish with extra chopped pistachios.