In a saucepan, melt the butter gently. Add the flour and stir thoroughly for 2 minutes. In a separate pan, heat the milk with the vanilla and bring to the simmer. Add the milk to the flour and butter, a bit at a time, stirring continuously to incorporate all the ingredients, until all the milk has been used. Remove from the heat, and add the egg yolks one at a time, beating the mixture until smooth. Keep aside and allow to cool slightly.
In a separate bowl whisk the egg whites to a snow with the sugar. Then fold into the flour and egg mix, carefully using a metal spoon. Grease the moulds with the butter, then dust with the sugar to prevent sticking. Spoon a tablespoon of treacle carefully into the base of each mould. Fill the moulds three-quarters full, with the sponge mix. Place onto a roasting tray. Then add hot water to around halfway up the mould and pace into a pre-heated oven at 180C – 350C and cook for approx 25 – 28 minutes.
When the puddings are ready, carefully remove, de-mould on to serving plates and drizzle with a little more treacle and serve with Chantilly custard.
For the custard
Place the milk and vanilla pod in a pan and heat gently (do not boil). Meanwhile place the egg yolks and sugar in the bowl and cream the two ingredients together until light, fluffy and the sugar has dissolved. When both are ready, remove the pod from the milk, cut in half and scrape out the seeds, placing them back into the milk. Gently pour the milk over the egg/sugar mix stirring all the time.
When all the milk has been used, pour the mix into the saucepan and return to the heat stirring continuously until the sauce starts to thicken, ensure that the sauce does not boil. If there are any lumps, pass the sauce through a sieve. When ready, whisk the whipping cream with sugar and the vanilla essence until light and just holding a peak. Add the whipped cream to the custard sauce, folding in to ensure it is kept light. Serve immediately