Heat the butter and oil in a frying pan over a moderate heat, saute the chicken for 15 minutes, then add the onions and garlic and saute for another 5 minutes or until softened. Cook the pasta as per pack instructions, adding the asparagus 1 minute before the cooking time is complete. Drain the pasta, reserving 75ml-125ml (3-4fl oz) of the liquid. Add to the pan along with the mascarpone, seasoning and zest. Stir to combine, then heat through. Sprinkle with parsley and serve immediately. NOTES : A quick and easy to prepare dish, comprising of pasta, asparagus,chicken and mascarpone cheese.