In a large skillet over medium heat, sauté onion, peas/carrots, and celery in olive oil with Italian seasoning, minced garlic, salt, and pepper until they are soft and the onion is translucent.
Meanwhile, cook the pasta according to package directions.
Once the veggies are done cooking, set aside in a bowl. Add butter to the same skillet and melt. Whisk in the flour until all the butter is absorbed. Increase the heat to medium-high and whisk in the broth and almond milk. Bring to a slow boil, then reduce heat to low. Add garlic powder, onion powder, nutritional yeast, Parmesan, and salt and pepper (to taste). Whisk and let the mixture simmer while the pasta cooks. Add veggies to the sauce mixture and stir. Strain the noodles, then add to the skillet and toss with the sauce. Add more salt and pepper, if needed. Serve with fresh parsley, if desired.