Process the Oreo cookies in a food processor until super fine crumbs form. Scoop out ½ cup of the crumb for the cookie dough and set it aside.
Heat the chocolate and the oil in the microwave in 20-second increments until smooth and melted.
Then mix 1 cup + 3 tablespoons of the processed Oreo crumbs into the melted chocolate until fully combined. Set aside to firm up for 10 minutes (this makes it easier to portion).
Then scoop 29 heaping teaspoons of the filling onto a parchment-lined tray or plate. Freeze until ready to use.
In a mixing bowl, cream the butter, sugar, and brown sugar together for 3 minutes.
Then mix in the egg, egg yolk, and vanilla extract.
Mix in the flour, oreo crumbs, baking soda, salt, and baking powder until almost combined. Then mix in the chocolate chips until just combined.
Scoop into two tablespoon-sized dough balls. Roll each ball between your hands until it's round, then flatten it between your palms.If you are having a hard time with the cookie dough sticking to your hands, chill it in the fridge for 10 minutes until it feels firmer. Add one of the portions of Oreo filling to the center. Fold the rest of the dough around it to seal it in.
Dip the top into a bowl of small chopped Oreo cookies and mini chocolate chips if desired, then place back on the tray.
Chill the pan in the freezer for 2-3 hours, overnight is best!
When you are ready to bake, preheat the oven to 350 F.
Space the cookies at least 2 inches apart, then bake for 12-14 minutes, or until the edges are a light golden brown. If the middle center is still domed, you can use the back of a measuring cup to gently press it down.
Let cool on a wire cooling rack, then enjoy!