Chop the dates quite small, place them in a bowl, and pour over 125ml boiling water. Leave for about 30 mins until cool and well-soaked, then mash lightly with a fork. Stir in 1 tsp vanilla extract.
Butter and flour five medium pudding tins and sit them on a baking sheet. Preheat the oven to 180C/fan 160C.
In a separate bowl, mix together the plain flour, baking powder, and bicarbonate of soda.
In a large bowl, beat the softened butter and brun farin together until slightly creamy (the mixture may be grainy).
Beat in the eggs one at a time, ensuring each is well incorporated before adding the next.
Add the treacle (sirup) to the creamed mixture. Alternately fold in the flour mixture and milk, starting and ending with the flour to avoid overbeating.
Stir the soaked and mashed dates into the batter, which might look slightly curdled but should be a soft, thick batter.
Spoon the batter evenly into the prepared tins and bake for 20-25 mins, until risen and firm.
While the puddings bake, combine the sugar, butter and half of the cream in a medium saucepan over medium heat. Stir until the sugar dissolves and the mixture is smooth. Add the treacle and let it bubble for a few minutes until thickened. Remove from heat and stir in the remaining cream.
Leave in the tins for a few mins, then loosen them well from the sides of the tins with a small palette knife before turning them out.
Add the sauce and let them sook up the sauce for at least an hour, but preferably overnight. Cover with a loose tent of foil so that the sauce doesn’t smudge (no need to chill).
When ready to serve, heat oven to 180C/fan 160C. Warm the puddings through, still covered, for 15-20 mins or until the sauce is bubbling. Serve them on their own, or with cream or custard.