Heat the oven to 180C/fan 160C/gas 4. Put the dates and tea in a pan, and bring to the boil. Gently cook for 3-4 minutes to soften the dates. Stir in the bicarbonate of soda.
To make the toffee sauce, put the sugar and cream in a pan with 150ml water. Stir, then put over a low heat and simmer until the sugar has dissolved. Cool a little.
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.