Bring a deep pan of salter water to the boil, tip in the pasta, reduce to a simmer and cook for 10 - 12 minutes or until the pasta is aldente. Drain and reserve the pasta in the pan with the lid on.

Finely chop the garlic and onion. Heat 2 tablespoons of the olive oil in a medium pan over a medium-high heat. Tip in the garlic and onions and fry for 3 - 4 minutes until the onions are soft and see-through. Halve and thinly slice the portobello mushrooms and tip into the pan. Cook the mushrooms until they are wilted and dark, about 4 - 5 minutes. Add the flour and nutritional yeast to the pan and stir well to coat the vegetables in the flour, cook for a further 2 minutes.

Pour in the rice milk and stir the pan ingredients, being sure to remove any debris from the bottom of the pan. Bring the rice milk to the boil and then turn the pan down to a simmer and cook until the sauce has thickened. Zest and juice the lemon. Chop the parsley and tip it into the pan along with half the juice of the lemon and cooked butter beans. Season the sauce to taste and lower the heat of the pan to just enough to keep the sauce warm.

Heat the remaining olive oil in a small frying pan on a high heat and toss in the asparagus spears. Fry the spears for about 4 - 5 minutes until they are soft and have an even colour on the outside.

Mix the sauce into the pasta and plate on individual bowls. Top with the fried asparagus and the lemon zest. Drizzle the remaining lemon juice over the dish to taste.