Preheat the oven
Set your oven to 350°F (175°C). Grease a medium ceramic or glass baking dish.
Make the batter
Whisk egg and sugar together until creamy. Stir in apricot jam and melted butter. Add milk and vinegar. Mix well.
Combine dry ingredients
In a separate bowl, sift flour, baking soda, and a pinch of salt. Add to the wet mixture and stir until smooth.
Bake the pudding
Pour the batter into your greased dish. Bake for 35–40 minutes, or until the top is deep golden and the center is set.
Prepare the sauce
While it bakes, combine butter, sugar, cream, hot water, and vanilla in a saucepan. Heat gently until butter melts. Do not boil.
Soak the pudding
When the pudding is out of the oven, poke holes across the top using a skewer or fork. Pour the warm sauce over the hot pudding slowly. Let it soak for 20–30 minutes before serving.
Serve warm
Best enjoyed with custard, whipped cream, or a scoop of vanilla ice cream.