Preheat oven to 350°F (175°C). Line two 6-inch pans with parchment and lightly grease sides.

In a bowl, whisk together: 220 g (1¾ cups) cake flour, 36 g (⅓ cup) black cocoa powder, 24 g (¼ cup) Dutch cocoa powder, 2 tsp baking powder, ½ tsp baking soda, and 1 ½ tsp fine salt.

Using a handheld mixer, beat 226 g (1 cup) unsalted butter until smooth.

Add 280 g (1⅓ cups + 2 tbsp) granulated sugar and beat 3–4 minutes until pale and fluffy.

Add 2 large eggs and 4 egg yolks (room temperature) one at a time, mixing well after each addition.

Mix in 2 tsp vanilla extract.

Add the dry ingredients in three additions, alternating with 240 ml (1 cup) whole milk, mixing on LOW just until combined.

Toss 10 finely chopped Double Stuf Oreo cookie wafers with 2 teaspoons flour, then fold into the batter.

Divide batter evenly between pans, filling each about ¾ full.

Bake 35–45 minutes. Start checking at 35 minutes, then check every 5 minutes until a toothpick inserted in the center comes out with moist crumbs (not wet batter).

Cool in pans 10 minutes, then remove and cool completely.

If assembling same day → ensure cakes are completely cool before torting.

If assembling next day → wrap and refrigerate before torting.

Torte each cake into 2 layers (4 total).

Heat-treat 30 g (¼ cup) cake flour by microwaving 30 seconds, stirring, then microwaving another 30 seconds. Let cool.

In a saucepan, whisk together: 240 ml (1 cup) whole milk, 80 g (⅓ cup packed) light brown sugar, 40 g (3 tbsp) granulated sugar, the cooled 30 g (¼ cup) flour, and ½ tsp fine salt.

Cook over medium-low heat, whisking constantly, until thick like cake batter.

Remove from heat and whisk in 40 g (3 tbsp) unsalted butter until fully melted.

Whisk in 24 g (¼ cup) black cocoa powder until smooth.

Stir in: 6 finely crushed Double Stuf Oreo cookie wafers, 2 tbsp Oreo cream, and 1 tsp vanilla extract.

Let cool until spoonable but not hot.

Using a handheld mixer, beat 345 g (1½ cups) unsalted butter until pale and fluffy.

Beat in 115 g (½ cup) full-fat cream cheese until completely smooth.

Add the Oreo cream from 30 Double Stuf Oreos and beat until fully emulsified.

Add: 150 g (1¼ cups) powdered sugar, 1½ tsp vanilla extract, and ⅜ tsp fine salt, and beat until smooth and fluffy.

Place first cake layer on your cake board. Add a small blob of frosting and spread it evenly across the surface.

Pipe a double frosting dam around the edge (go around twice to create a higher barrier).

Add about four 3-Tbsp scoops of Oreo batter filling into the center.

Smooth evenly.

Repeat with remaining layers.

Use a bench scraper to remove any excess frosting that pushes out along the sides.

Chill the cake for 30 minutes to firm up.

Frost the cake with remaining buttercream and smooth with a bench scraper.

Add dollops of remaining Oreo batter filling randomly onto the sides.

Gently scrape again to create the marbled Oreo ripple effect. Do not overwork.

Top generously with hand-crushed Double Stuf Oreos.

Chill 30 minutes before slicing for clean cuts.