Cook pasta according to instructions.
In a large saute pan, over medium heat, add frozen spinach. Cook for 5-7 minutes stirring occasionally to thaw.
Once the spinach is thawed add artichokes, garlic, onion powder, crushed red pepper, vegetable stock, and parsley.
Stir and bring to simmer over medium-high heat for 5 minutes.
Add almond or soy milk and nutritional yeast; stir. Reduce heat to medium.
In a small bowl mix together cornstarch/flour and water. Add to the saute pan and stir.
Continue to cook over medium heat for 10 more minutes, allowing the sauce to thicken, stirring occasionally.
Add sour cream, salt, and pepper if desired. Stir.
Cook for 2 more minutes.
Pour over cooked pasta and serve.