Plan for Making this Cake
1. Bake the cake layers. The cake layers can be made in advance and refrigerated or frozen. Layers should be completely cooled prior to assembling the cake
2. Make the Oreo filling
3. Stack the cake
4. Make the chocolate frosting
5. Frost and decorate the cake

For the Oreo Chunks
Remove 4 Oreos from the package for decorating the top of the cake.

Chop one row of the Oreos (1/4th of them), and set aside for the filling.

Chop one row of Oreos (1/4th of them), and toss with 1 Tbsp flour for the Oreo Layer and set aside.

Chop the remaining two rows of Oreos (1/2 of them), and toss with 2 Tbsp flour for the chocolate layers and set aside.

Oreo Cake Layer
Preheat over to 350F.

In a large bowl cream the butter until fluffy, about 3-5 minutes. Add the milk and vanilla and mix to combine.

In a separate bowl mix together the flour, baking powder, and salt.

Add the dry ingredients to butter mixture. Mix until integrated. Stir in sugar. With an electric mixer on low speed, beat for 30 seconds. Turn the mixer up to medium speed and beat for 2 minutes. Add the egg whites. Beat for 2 more minutes. Stir in the quartered cookies.

Bake for 25-30 min. Cool in the pans for 30 minutes, then turn them out onto a cooling rack and cool completely.

For the Chocolate Cake Layers
Preheat the oven to 350. Butter 2 (8-inch) round cake pans. Line with parchment paper, then butter and flour the pans.

Sift the flour, sugar, cocoa, baking soda, baking powder, and salt into the bowl of an electric mixer fitted with a paddle attachment and mix on low speed until combined.

In another bowl, combine the buttermilk, oil, eggs, and vanilla.

With the mixer on low speed, slowly add the wet ingredients to the dry. With mixer still on low, add the coffee and stir just to combine, scraping the bottom of the bowl with a rubber spatula.

Stir in the Oreo chunks.

Pour the batter into the prepared pans and bake for 35 to 40 minutes, until a cake tester comes out clean. Cool in the pans for 30 minutes, then turn them out onto a cooling rack and cool completely.

For the Oreo Filling
Using an electric mixer with a whisk attachment, beat the cream cheese, vanilla, and sugar until light and creamy. Beat in 1/4 cup whipping cream until smooth. Add the rest of the cream and beat until it has the consistency of whipped cream (don’t overmix).

Reserve 1/2 cup to use to decorate the top of the cake. Place in the refrigerator until ready to use.

Stir in the reserved Oreo chunks into the remaining whipped cream mixture. Immediately spread filling on top of the Oreo layer and one of the chocolate layers.

For the Chocolate Frosting
Chop the chocolate and place it in a heat-proof bowl set over a pan of simmering water. Stir until just melted and set aside until cooled to room temperature.

In the bowl of an electric mixer fitted with a paddle attachment, beat the butter on medium-high speed until light yellow and fluffy, about 3 minutes.

Add the egg yolk and vanilla and continue beating for 3 minutes.

Turn the mixer to low, gradually add the confectioners' sugar, then beat at medium speed, scraping down the bowl as necessary, until smooth and creamy.

Dissolve the coffee powder in 2 teaspoons of the hottest tap water. On low speed, add the chocolate and coffee to the butter mixture and mix until blended. Don't whip! Spread immediately on the cooled cake.