Pre-heat oven to Gas Mark 1/2 , 100°C (225°F). Line baking sheet with non-stick paper. Whisk the egg whites until stiff, add half the sugar, slowly whisking until completely dissolved, then lightly fold in the remaining sugar with a metal spoon. Pipe or spoon the mixture into small circular shapes and bake in oven for approximately 11/2 hours to dry without colouring. Cool and store, until required, in an airtight container. Make up Ice-Cream: See ice-cream pudding recipe, leave out the fruit. Make up Cranberry Sauce: Combine cranberries, sugar and water and simmer until the berries are just soft, set aside to cool. To Assemble the Terrine: Line a loaf tin with overlapping cling film. Break up the meringues and fill the bottom of the tin. Add half of the ice-cream, then spread two tablespoons of cranberry sauce on top. Cover with remaining ice-cream. Close with overlapping clingfilm and freeze.
Turn the terrine onto a serving plate, remove cling film. Slice and serve with remaining cranberry sauce, which has been heated up with the port.