To the same pot, or to a rimmed skillet, melt vegan butter over medium heat. Add minced garlic and cook for 2 minutes, stirring often, until lightly golden.
Turn the heat to medium-low and add the flour, whisking until a paste has formed. Slowly start pouring the milk, whisking constantly to prevent clumps, until creamy.
Add dijon mustard, garlic powder, nutmeg (optional), salt, black pepper, and lemon juice. Stir.
Add nutritional yeast, and shredded vegan cheese and mix. Cook for 2-3 minutes or until the cheese has fully melted. Add a splash of milk or water if the cheese sauce is getting too thick. Once ready, remove from the heat.
Add the cooked pasta and peas, and using a spatula, carefully toss until everything is well coated. Taste and adjust the flavor if needed, adding more salt for saltiness, lemon juice for tanginess, or black pepper to taste. Serve!