Preheat the oven to 180°C, fan 160°C, gas 4. Lightly butter a 20 x 30cm traybake tin at least 2.5cm deep.
Put the dates on a chopping board and roughly chop, then put in a medium pan with 250ml boiling water. Bring to the boil then cook for 2-3 minutes to just soften the dates. Pour into a large shallow bowl and mash with a fork.
Put the butter and sugar in a mixing bowl and beat until light and creamy; gradually add the eggs and beat well. Add the bicarbonate of soda to the dates – it will foam up – stir well, then add to the cake mixture with the flour, spice and vanilla, and beat with a wooden spoon until combined.
Pour the mixture into the tin and bake for 25 minutes or until the mixture feels firm to the touch in the centre.
Meanwhile put all the sauce ingredients into a medium pan and bring to the boil. Cook for 1-2 minutes until thickened slightly. Allow to cool then reheat when ready to serve. Drizzle a little over the top of the pudding and serve the remainder alongside it in a jug.
