Preheat oven to 180 degrees C. Beat butter with sugar until light and creamy. Add egg beat well. Add custard powder and vanilla mix. Then add flour sifted with baking powder and baking soda if using, gradually until a soft dough forms.
Roll 1 tbsp. full of dough into balls, place on greased baking trays, press down a bit with a fork then bake for 12-15 mins, don’t let it brown. Cool on trays for 2 mins then put on wire racks to cool completely. Enjoy with tea or coffee!