In large skillet, saute onion until soft, adding small amounts of water to unstick. Add garlic and sauté 1-2 minutes.
Add mushrooms to skillet and cook until just soft.
Add sun-dried tomatoes, chili flakes, and spinach, and cook until spinach has just begun to wilt.
Meanwhile, in blender process non-dairy milk and cashews.
To skillet add marinara sauce and milk/cashew mixture and stir until well combined. Cook until warmed through over medium heat. Salt and pepper to taste.
Stir in chopped basil, add sauce to noodles and mix until combined.