Preheat the oven to fairly hot 200 °C (Gas Mark 6, 400 °F).

Melt the butter in a frying-pan. Add the onions and garlic and fry until the onions are soft. Remove from the heat and transfer the mixture to a bowl. Set aside to cool.

When the mixture has cooled, stir in all the remaining ingredients and mix and beat until they are thoroughly blended. Spoon into a well-greased 1 kg (2 lb) loaf tin, smoothing the top with a knife.

Put the tin into the oven and bake the loaf for 1 hour, or until a skewer inserted into the centre comes out clean.

Remove from the oven and pour off any fat. Turn out on to a warmed serving dish and serve at once, if you are serving the loaf hot.