Preheat oven to 180C/350F/Gas Mark 4. Grease and line a 20cm/8 inch square cake tin.

Put the dates in a small pan with the boiling water and baking soda. Heat gently for about 5 minutes, without boiling, until the dates are soft.

Using a standmixer, cream the butter and caster sugar until light and fluffy. Beat in the egg, vanilla and date mixture.

Fold in the flour using a metal spoon, mixing evenly. Pour the mixture into the prepared cake tin. Bake in the preheated oven for 40-45 minutes, or until firm to the touch and just starting to shrink away from the sides of the tin.

For the toffee sauce , combine the brown sugar, butter and cream in a saucepan and heat gently until dissolved. Simmer gently, stirring, for about 2 minutes.

Remove the cake from the oven and prick all over the surface with a skewer or fork. Pour the hot toffee sauce evenly over the surface. Leave it to cool in the tin, then cut into squares.