Mix together the nuts, breadcrumbs and herbs. Fry the onion in the oil and add to the mixture. Melt the yeast extract in hot water and add to the mixture along with the margarine. Season to taste and mix well.
Mix the cold water into the sausage mix and leave for 10 minutes. Fry the onion in oil add, along with the tomato puree, to the sausage mixture.
Grind the breadcrumbs with the fresh parsley, for colour, and mix with the other third layer ingredients.
Assembly and cooking
Put approximately 2 thirds of the first layer in the bottom and up the sides of the tin. Add second layer followed by the third layer. Finish with the remainder of the first layer. When cut it will show three colours.
Cook for approximately 1½ hours in a moderate oven, 180°C/350°F/Gas 4. Allow to stand for 10 minutes then remove paper. Meanwhile, liquidise together all the orange sauce ingredients and heat until fully thickened to serve with the roast.