Beat together the butter and sugar with electric beaters until creamy, then beat in the eggs, flour and mixed spice. Stir in the date mixture and pour into a buttered 20cm x 30cm ovenproof dish. Pour the toffee sauce over the top. Don’t worry if it looks messy. The sauce will sink to the bottom and a sponge will form on top. Bake for 30-35 minutes or until the top is just firm to the touch. Scoop onto plates and serve with ice cream.