Chop the Oreo cookies; set aside. Spray an 8" square pan with non stick cooking spray. Preheat your oven to 350 degrees.
Melt butter in a large glass bowl in the microwave. Whisk in the cocoa powder until smooth.
Add the sugar, eggs, and vanilla and whisk until blended.
Stir in the flour and salt. Mix in the chocolate chips and about 1 1/4 cups of the chopped Oreos. (Save the other 3/4 cup for the top.)
Spread the brownie batter into the prepared pan. Sprinkle the 3/4 cup of cookie pieces over the top.
Bake at 350° for 30-35 minutes or until a toothpick inserted in the middle comes out with moist crumbs, but not batter.
For easiest slicing, let the brownies cool for at least an hour.
If desired, melt the white chocolate and the oil in a double boiler, or at 30% power in the microwave, stirring every 30 seconds. Drizzle over the brownies.