Heat the oil in a frying pan, add the mushrooms and cook over a high heat, stirring frequently, for 2 minutes until browned and softened. Add the tofu and cook, stirring, for 1 minute.
Add the tomatoes to the pan and cook for 2 minutes until starting to soften. Stir in the mushroom ketchup and half the parsley and season with salt and pepper.
Serve immediately with hash browns, sprinkled with the remaining parsley.