Place a rack near the lower third of the oven and preheat the oven to 350 degrees F. Grease 9-inch pie dish (or cake pan) and set aside.Combine the flour, salt and baking powder in a bowl. Set aside.
In another bowl, beat the butter and coconut oil for 2 minutes on medium speed (hand mixer/kitchenaid) until completely smooth and creamy.
and continue to beat on medium speed until creamy, about 1 minute.
Add in the egg, egg yolk, and vanilla on medium speed until just combined. Scrape the sides as and when required.
On the low speed setting, slowly mix in the dry ingredients
until just combined. Do not overmix.
Stop the mixer, using a rubber spatula, fold in ½ cup of the chopped candy bars along with most of the chocolate chips (reserving about 1 - 2 tablespoons for the topping).
Press the cookie dough evenly into the prepared pie dish.
Top the cookie cake batter with the remaining ¼ cup of chopped candy bars and the 2 tablespoons of chocolate chips.
Bake for 25 - 30 minutes or until the cake is lightly golden brown (could be up to 35 minutes depending on your oven).
Cover the cake loosely with aluminum foil after the first 15 minutes of baking to avoid excess browning.
Remove from the oven and set the pie dish on a wire rack to allow cookie cake to cool completely. Use a sharp knife to slice, once cooled.