Preheat oven to 175°C. Line a baking sheet with baking paper, set aside.
In a large bowl, cream butter and sugar together, and beat until smooth (for about 3 minutes). Beat in the vanilla and the egg. Add in 2 cups of flour, baking powder and salt. Mix until well combined. Then add the rest of the flour until the mixture becomes a stiff cookie dough.
Turn dough out onto a clean surface. Lightly wet your hands and knead the dough until it forms a soft ball. Wrap dough with plastic wrap and chill in the refrigerator for 30 minutes.
Divide dough in half, then roll out about half a cm thick onto a lightly floured surface. Cut using any cookie cutter shape you like, and transfer immediately onto baking sheet. Bake for 6-8 minutes or until just set. For crispier golden edged cookies, bake for up to 9 minutes. Allow to cool on the cookie sheet (they should be soft) for 5 minutes before transferring to a cooling rack to cool completely.