Preheat oven to 180°C (160°C fan-forced). Line 2 baking trays with baking paper. In a bowl, beat butter and sugars until well combined. Beat in egg and vanilla.
In a separate bowl, whisk the flour and baking powder until well combined. Stir half the flour into the creamed butter and gently stir until fully combined. Repeat with remaining flour. Stir in milk choc chips. Roll heaped tablespoonfuls of mixture into balls and place on trays approx. 3cm apart. Lightly press down.
Bake for 15 minutes or until lightly golden. Transfer to a wire rack to cool. Store in an airtight container for up to 1 week.