Let’s bake and assemble this decadent cake:

1. Preheat Oven and Prepare Pan:

• Preheat your oven to 350°F (175°C).
• Grease and flour a 9×13-inch baking pan thoroughly.

2. Prepare the Cake Batter:

• In a large mixing bowl, combine the dry yellow cake mix powder, sour cream, vegetable oil, room temperature eggs, dry instant vanilla pudding mix, 1 cup crushed Oreos, 1 teaspoon vanilla extract, milk, and ¼ cup granulated sugar.
• Mix with an electric mixer on low speed for about 30 seconds to combine, then beat on medium speed for 2 minutes (or according to your cake mix instructions for a doctored mix), until the batter is well combined and smooth. Scrape down the sides as needed.

3. Make the Cinnamon Swirl Mixture:

• In a small bowl, combine the packed brown sugar and ground cinnamon. If using, stir in the ½ cup of optional crushed Oreos for the swirl. Mix well.

4. Layer and Swirl the Cake:

• Pour half of the prepared cake batter into the greased and floured 9×13-inch baking pan, spreading it into an even layer.
• Sprinkle half of the cinnamon-sugar (and Oreo, if using) mixture evenly over this batter layer.
• Carefully pour the remaining cake batter on top, spreading it gently to cover the cinnamon swirl.
• Sprinkle the remaining cinnamon-sugar mixture evenly over the top of the batter.
• Using a knife or a skewer, gently swirl the batter and cinnamon mixture together. Make a few passes in S-shapes or figure eights, but don’t over-swirl, or you’ll lose the distinct marbled effect.

5. Bake the Cake:

• Place the pan in the preheated oven. Bake for 30-35 minutes, or until a wooden toothpick inserted into the center of the cake comes out clean.
• Allow the cake to cool in the pan on a wire rack for about 10-15 minutes.
• Then, if desired (or if your pan isn’t attractive for serving), carefully invert the slightly warm cake onto a wire rack to cool completely. If serving from the pan, just let it cool completely in the pan. Ensure cake is 100% cool before frosting.

6. Prepare the Oreo Cream Cheese Icing:

• In a large, clean, chilled mixing bowl, pour in the 2 cups of very cold heavy whipping cream. Beat with an electric mixer (whisk attachment) on medium-high speed until soft peaks form.
• In a separate large bowl, beat the softened cream cheese with an electric mixer (paddle attachment or regular beaters) until completely smooth and fluffy.
• Add the 1 teaspoon vanilla extract, 2 cups sifted powdered sugar, and 1 teaspoon ground cinnamon to the cream cheese. Beat on low speed until combined, then increase to medium-high and beat until smooth and creamy.
• Gently fold the prepared whipped cream into the cream cheese mixture using a rubber spatula until just combined and no streaks remain. Be careful not to overmix and deflate the whipped cream.

7. Frost and Garnish the Cake:

• Once the cake is completely cool, spread the prepared Oreo Cream Cheese Icing evenly over the top (and sides, if removed from pan and desired).
• Sprinkle the ½ cup of crushed Oreos (and optional white chocolate chips) over the top of the icing for added crunch and decoration.
• Chill briefly before serving if desired, or serve immediately.

A beautiful, flavorful cake ready to be enjoyed