Preheat the oven to 350°F (175°C). Line 2 large baking sheets with baking or parchment paper; set aside.
Beat together the butter and peanut butter until creamy. Add in both sugars and vanilla extract, beating again until smooth. Beat in the egg until well combined.
Fold in the flour, baking powder and salt (be careful not to over-mix), until a smooth cookie dough forms. Then, add in half of the chocolate chips and mix them through with your fingers, or a wooden spoon.
Roll the dough into about 15 balls and arrange them on lined baking sheet. Press the remaining chocolate chips onto the tops of each cookie; bake for about 10-11 minutes, until tops are golden (do not over bake or they will dry out and become tough).
Allow to cool on a wire rack for about 15 minutes.