Preheat oven to 180°C.

In a bowl, mix together flour, salt and baking soda. Set aside.

In another bowl, cream together butter, sugar and vanilla essence.

Add milk and beat until combined.

Now add the flour mixture and beat the mixture until incorporated.

Add milk by table spoons if needed. You need a crumbly dough, not a soft one.

Take the dough between parchment sheets and roll it into a thin disc.

Cut out circles out of it and arrange them on a greased baking tray. 

With the help of a smaller cookie cutter, make a concentric circle inside the cut egde.

Use a fork to make some indentations on the biscuit.

Bake for 8-10 minutes. They may be a bit soft when coming out of oven, but they will crisp up once cool.

Store in airtight jar and enjoy with a cup of coffee or tea.