Heat the butter and olive oil in a large frying pan. Fry the onion and garlic for 2 minutes, add the mushrooms and thyme and fry for a further 5 minutes. Stir in the Bisto Original Gravy Powder and add 1 cup (250 ml) boiling water. Stir until sauce is thickened.
Add the cream and simmer gently for 10 minutes. Toss in the cooked pasta and peas. Serve topped with chopped parsley and cheese.