Preheat oven to 400 degrees Fahrenheit. In a very large oven-proof skillet over medium heat, add 2 tablespoons of vegan butter with sliced mushrooms. Cook until the mushrooms release their water, and have browned on both sides, 5 - 7 minutes. Season with ½ teaspoon salt, mix well, then remove to a plate and reserve.

To the pan, add in the remaining vegan butter, shallot, and garlic, cooking under medium heat, until the shallot is translucent, about 3 minutes. Add in the remaining salt and flour, whisking until everything is combined well, and the flour has cooked; about 1 minute.

Slowly add in the plant milk while whisking, to prevent the mixture from clumping. Add in the vegetable stock, turn the heat to medium-high, and whisk until the mixture thickens, about 5 minutes. Add the nutritional yeast, and parsley. Mix well.

Add the mushrooms and spaghetti to the pan, breaking the pasta in half before adding. Mix to coat, and cook until the spaghetti has softened slightly, mixing frequently; about 3-5 minutes.

Sprinkle the panko on the top of the pan, remove from the stove, and bake in the oven for 15 minutes, until bubbly, and the breadcrumbs have browned. Remove from oven, and let rest for 10 minutes before dividing among 6 containers. Serve with green salad and tomatoes. Store in your MPOF meal prep containers.