Place the 125ml of the evaporated milk into a jug and stir in the bicarbonate of soda. Stir the remaining evaporated milk into the sauce mixture.

Sift the dry ingredients over creamed butter mixture. Pour the bicarbonate of soda and milk mixture over the top. Carefully fold the mixture together. Stir in the vinegar and spoon into an ovenproof baking dish.

Place all of the ingredients in a pan (including the additional evaporated milk) and cook for 4-5 minutes, stirring, until smooth and combined.

Preheat the oven to 180°C. Cream the butter and sugar together in a mixing bowl. Add the egg and beat well. Stir in the jam.

Pour half of the sauce mixture over the batter and bake for 25 – 30 minutes, or until the sponge is just cooked. Pour the remaining sauce over the top and serve with cream, ice cream or custard.