Line 2 cookie sheets with parchment paper or silpat mats.
In a bowl, combine the dry ingredients: flour, baking powder, and salt. Set aside.
In another bowl, using a hand mixer beat the butter with the sugar until smooth and creamy (2-3 minutes). Add in the egg, egg yolk, and vanilla extract, and mix again until smooth.
Add in the dry ingredients and mix until just combined, then gently fold in the chocolate chips.
Scoop out the cookie dough into 24 even balls, and place onto one of the lined baking sheets.
Flatten the balls slightly with your fingers, then place an oreo over half of the dough pieces, and cover with the other pieces. Very carefully roll each sandwich into a smooth cookie dough ball with the Oreo in the center.
Place in the fridge for 30 minutes and preheat the oven to 350°F/180°C.
Make sure that the cookies are placed about 2 inches apart (you will likely need both trays, the cookies are big!), then bake for 14-16 minutes or until the edges start turning golden brown. Remove from the oven, and allow to cool on the cookie sheet for 10 minutes then transfer to a wire rack to cool completely.