For the cake:
1/2 cup unsweetened cocoa powder + 1 tablespoon for dusting
3/4 cup boiling water
6 tablespoons whole milk
1 teaspoon vanilla extract
1 1/2 sticks of unsalted butter, softened
3/4 cup light brown sugar
3/4 cup granulated sugar
1 teaspoon baking soda
1/2 teaspoon salt
1 1/2 cups all-purpose flour
For the Kit Kat bar:
3 cups semisweet chocolate chips
1/2 cup heavy cream
1 1/2 cups white chocolate chips
1/2 cup coconut oil
24 wafer sandwich cookies with vanilla filling
For the cake: Preheat the oven to 350°F. Spray a 9 1/4" x 5 1/4" x 2 3/4" loaf pan with oil and dust with 1 tablespoon of cocoa powder.
In a small bowl, whisk the boiling water with the cocoa until mixed and smooth. Add milk and vanilla extract.
In a large bowl, beat the butter, brown sugar, and white sugar together until fluffy, about 4 minutes. Add one egg at a time, mixing thoroughly between each addition. On the lowest setting, add the baking soda, salt, and one third of the flour mixture. Mix until well incorporated. Add half of the cocoa mixture. Alternate adding the two mixtures, ending on the flour mixture.
Pour the batter into the loaf pan and bake for 40-45 minutes or until a toothpick comes out clean when testing it.
Allow to cool and cut off the rounded top off of the loaf using a bread knife to create a flat surface.
For the Kit Kat: Line a 9 1/4" x 5 1/4" x 2 3/4" loaf pan with plastic wrap. Melt 1 1/2 cups of semisweet chocolate chips and pour into the bottom of the pan. Place in freezer for 5 minutes to set.
To make white chocolate ganache, heat up heavy cream in the microwave in 30-second intervals until simmering. Pour over white chocolate chips. Let sit for 2 minutes to melt, then whisk together.
Starting with the white chocolate ganache, alternate layers of ganache and cookies, ending with ganache. Place in freezer for 10 minutes to set.
Pull the cookie base out of the pan and place on a sheet pan, milk chocolate side down. Flip the cake upside down and place on top of the chocolate cookie base.
Microwave remaining chocolate chips and coconut oil in 15-second increments until chocolate is melted and the mixture is smooth. Stir in between each session. Pour the melted chocolate as evenly as possible over the top of the cake, making sure it covers the sides too. Place in freezer for 10 minutes, or until set, and enjoy!