1. Preheat the oven to 350°F (180°C). Line two 8 inch round cake pans with parchment paper, leaving a little overhang for easy removal, and lightly grease the parchment and sides.

2. In a medium bowl whisk together the all purpose flour, baking soda, baking powder, and fine sea salt until well combined, then set aside.

3. In a large mixing bowl stir the melted butter with the light brown sugar and granulated sugar until glossy and smooth. Add the eggs and vanilla extract and mix until the mixture is thick and well blended.

4. Fold the dry ingredients into the wet ingredients just until no streaks of flour remain, then gently stir in the semisweet chocolate chips and mini M&Ms.

5. Divide the cookie dough evenly between the prepared pans and press into a level layer with your fingertips or an offset spatula.

6. Bake the cookie layers for 18 to 22 minutes, or until the edges are golden and the centers are just set but still soft. Cool the pans completely on a wire rack, then place the cookie layers in the freezer for 30 minutes to firm up.

7. While the cookies chill, remove the vanilla ice cream from the freezer and let it sit at room temperature for 15 to 20 minutes until soft enough to stir but not melted.

8. Scoop the softened ice cream into a large bowl and fold in the chocolate chip cookie dough bites or chopped cookies, mini M&Ms, and crushed chocolate sandwich cookies until evenly distributed.

9. Line one of the cooled cake pans with plastic wrap, letting it hang over the sides, and spread the ice cream mixture into the pan in an even layer. Cover the top with plastic wrap and freeze for 2 to 3 hours, or until very firm.

10. To assemble, place one frozen cookie layer on a serving plate or cake stand, top side up. Unwrap the ice cream layer, place it on top of the cookie base, and peel away the plastic wrap.

11. Set the second cookie layer on top of the ice cream, top side down, pressing gently to help everything adhere. Smooth any ice cream that squishes out the sides with an offset spatula and freeze the assembled cake for 1 to 2 hours, until solid.

12. For the ganache, place the semisweet chocolate chips in a heatproof bowl. Heat the heavy cream in a small saucepan or microwave until just simmering, then pour it over the chocolate and let stand for 2 to 3 minutes.

13. Stir the chocolate and cream together until completely smooth and glossy, then add the light corn syrup or neutral oil if using and stir again. Let the ganache cool until it is thick but still pourable, similar to warm hot fudge.

14. Remove the cake from the freezer and pour some ganache onto the center of the top layer. Use an offset spatula to gently nudge it toward the edges, allowing it to drip decoratively down the sides.

15. While the ganache is still soft, scatter the mini chocolate chip cookies, crushed chocolate sandwich cookies, and M&Ms over the top of the cake, pressing lightly so they stick.

16. Return the cake to the freezer for at least 30 minutes to fully set the ganache and toppings before slicing and serving.