Line a 9x13" baking dish with parchment paper, leaving extra overhang on the sides for easy removal. Spray with nonstick cooking spray. Make brownies according to package instructions, then pour brownie batter into prepared pan. Bake as directed. Allow to cool completely.

Place the chocolate chips into a medium bowl. Pour heavy cream into a glass measuring up and heat in the microwave until it just begins to boil. Pour hot cream over the chocolate chips, then cover with plastic wrap. Allow to sit for 5 minutes before removing the plastic wrap and stirring until smooth.

In a stand mixer fitted with the paddle attachment, cream the butter and both sugars together until light and fluffy, about 3 minutes. Add the vanilla, flour, salt, and milk, beating until combined. Stir in the chocolate chips; set aside.

Once brownies are completely cool, spread the ganache evenly on top. Scoop the cookie dough evenly over the ganache, then use a rubber spatula or your fingers to gently press the filling into an even layer. Chill in the freezer for at least 2 hours.

Run a knife along the edges of the pan to loosen the brownies. Using the parchment sides, gently lift the brownies out of the pan and onto a cutting board.

Dip a sharp knife in hot water, wipe clean with a towel, then slice into the brownies. Try to aim for 1-inch cubes, warming and cleaning the knife between cuts. Once all of the cubes have been cut, return to the freezer while you prepare the chocolate.

Place the chocolate and oil in a medium microwave-safe bowl, and heat in the microwave until smooth and melted--I recommend removing the chocolate and stirring every 30 seconds so that you don't risk burning the chocolate**.

Line a large cookie sheet with parchment or wax paper. To dip the brownie bites, place one on a fork, and lower it into the chocolate. Use the fork to pour the chocolate over the brownie bite, so that it gets completely covered. Use the fork to lift the brownie bite out of the chocolate, gently tapping the handle of the fork on the edge of the bowl to get rid of any excess chocolate, then place it onto the lined cookie sheet. You might need to use another fork to push the brownie bite off of the other fork. Repeat with the remaining brownie bites, then place in the refrigerator until chocolate has set.

Place the white chocolate and 1 teaspoon coconut oil in a small microwave-safe bowl, and heat in the microwave until smooth and melted. Do the same with the milk chocolate and remaining teaspoon of coconut oil.

Using a fork, drizzle the white chocolate over half of the brownie bites. Drizzle the other half with the milk chocolate. Return to the refrigerator for a few minutes to allow the drizzle to set up.

Store brownie bites in an airtight container in the refrigerator for up to one week.