Preheat the oven to moderate 180°C (Gas Mark 4, 350°F). Lightly grease a large baking dish with the butter, then sprinkle over the breadcrumbs.

Put the sultanas or raisins and candied peel in a small bowl. Cover with rum and set aside to soak for 10 minutes.

Using the back of a wooden spoon, rub the ricotta through a strainer into a large bowl. Beat in the eggs, then gradually add the sultana or raisin mixture and all of the remaining ingredients.

Turn the mixture into a baking dish and put the dish into the oven. Bake for 45 minutes to 1 hour, or until the top is light brown. Remove from the oven and set aside to cool. When the mixture is cold, transfer it to the refrigerator and chill for at least 1 hour.

To serve, run a knife around the edge of the dish and quickly invert the mixture on to a serving dish.