Cream together the butter and sugar until smooth and even.
In a separate bowl, mix the milk, eggs, vinegar and vanilla seeds.
Gradually add the contents of the second bowl to the first, stirring all the time.
Now add the sieved flour and baking soda, a little at a time, until the mixture is thick and even.
Spoon the mixture into the special muffin trays (lined with paper cases) and bake in the oven at 180°C for approximately 20 minutes.