Mix cream, milk, and vanilla seeds in a heatproof bowl over simmering water without letting the bowl touch the water.
Beat egg yolks and sugar until fluffy, then stir in the warm cream mixture.
Cook the mixture over simmering water while stirring until thick enough to coat a spoon, then cool.
Churn the mixture in an ice cream maker for 40 minutes or until set.
Preheat the oven to 190°C and grease a 20cm square cake tin with butter and flour.
Whisk the butter and sugar together until well blended.
Mix in the golden syrup, treacle, vanilla, and eggs before gradually folding in the flour.
Boil the dates in 300ml of water in a saucepan.
Purée the hot date mixture in a blender, stir in bicarbonate of soda, and quickly combine with the batter.
Pour batter into the tin and bake for 40-45 minutes until the top is firm.
Simmer butter, brown sugar, and syrup until dissolved, then stir in lemon juice and double cream.
Serve warm pudding slices with the prepared sauce and ice cream.