Step 1: Prepare the Whipped Cream
1. In a large mixing bowl, whip the heavy cream until soft peaks form.
2. Gradually add 1/2 cup powdered sugar and vanilla extract, continuing to whip until stiff peaks form. Set aside.

Step 2: Make the Cream Cheese Mixture
1. In another bowl, beat the softened cream cheese until smooth.
2. Gradually mix in 1 cup of powdered sugar until well combined.

Step 3: Combine Mixtures
1. Gently fold the whipped cream into the cream cheese mixture until fully combined. Be careful not to deflate the whipped cream.

Step 4: Assemble the Cake
1. In a 9×13-inch baking dish, arrange a layer of Oreo cookies at the bottom. You can dip them in milk briefly for extra softness if desired.
2. Spread half of the cream cheese and whipped cream mixture over the layer of cookies.
3. Add another layer of Oreo cookies on top of the filling, followed by the remaining cream cheese mixture. Finish with a final layer of Oreo cookies on top.

Step 5: Chill the Cake
1. Cover the baking dish with plastic wrap or aluminum foil and refrigerate for at least 4 hours, or overnight for best results.

Step 6: Serve
1. Before serving, garnish with chocolate shavings or crushed Oreos if desired.
2. Cut into squares and serve chilled. Enjoy your delicious Oreo Icebox Cake!