Preheat oven to 200 degrees C. Grease a pie dish. Heat the oil in a frypan, brown the onion then add the chicken and cook, stirring, till browned. Stir in the crumbled stock cube. Add the peas and corn, then add the tin of soup and mix well. Season with the salt, pepper and rosemary
Line dish with puff pastry and add the filling then top it with pastry. Bake for 20-30 mins till the top is golden.