Use a tofu press to press 1 block extra-firm tofu (optional but recommended to prevent the final dish from turning out watery).
Once the tofu is done pressing, preheat the oven to 350 degrees Fahrenheit.
Slice the extra-firm tofu widthwise into pieces about 1/4 inch thick.
Stack a few slices (stacking is just to save time), then cut them into short, thin strips (these act as a noodle replacement in this dish). Repeat until the whole block is cut.
Add 1 1/4 cups silken tofu or soft tofu, 1/3 cup unsweetened soy milk, 1/4 cup nutritional yeast, 1/2 teaspoon onion powder, 1/2 teaspoon salt, 1/8 teaspoon black pepper, 1 tablespoon Dijon mustard, and 1 small pinch of nutmeg (optional) to a blender, then blend until smooth.
Transfer the blended sauce and the sliced extra-firm tofu to a mixing bowl, then gently stir to coat the tofu in the sauce.
Transfer that mixture to an 8-inch baking dish, then spread in an even layer.
Sprinkle shredded vegan cheese on top, if desired.
Bake for 30 minutes or until hot and bubbling, then let rest for 10 minutes before serving.