Cook the pasta according to package instructions until al dente. Drain and set aside.
In a large skillet, heat the olive oil over medium heat. Add the sliced onions and cook, stirring frequently, until they are caramelized and golden brown, about 15-20 minutes.
Add the minced garlic, dried thyme, salt, and black pepper to the skillet. Cook for an additional 2 minutes until fragrant.
Pour in the vegetable broth, almond milk, and soy sauce. Stir well to combine.
Bring the mixture to a simmer and add the nutritional yeast. Stir until well incorporated.
Mix the cornstarch with water to create a slurry, then add it to the skillet. Stir continuously until the sauce thickens, about 2-3 minutes.
Add the cooked pasta to the skillet and toss to coat in the creamy sauce. Cook for an additional 2 minutes to heat through.
Serve hot, garnished with chopped fresh parsley.