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Layers of oatmeal cookies, peanut butter oatmeal cookie dough, a peanut butter mousse and MnMs. This overhead shot shows the top of the icebox cake

No-Bake Monster Cookie Icebox Cake

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  • Author: Julianne Dell
  • Prep Time: 30 min
  • Cook Time: 4 hours
  • Total Time: 4 hours 30 minutes
  • Yield: 8-10 slices


This No-Bake Monster Cookie Icebox Cake is layers of oatmeal cookies with a peanut butter mousse and a homemade peanut butter and oatmeal monster cookie dough. Topped off with MnMs and whipped cream.


  • 1 package (12.5oz) Oatmeal Cookies
  • 1 cup MnMs

For the peanut butter mousse:

  • 1 ½ cups heavy whipping cream
  • ¾ cup powdered sugar
  • 8 ounces cream cheese, at room temperature
  • ¼ cup creamy peanut butter
  • ¼ cup granulated sugar
  • 1 teaspoon vanilla extract

For the cookie dough:

  • 4 tablespoons unsalted butter, softened
  • 3 tablespoons granulated sugar
  • 3 tablespoons light brown sugar
  • ½ cup creamy peanut butter
  • ½ teaspoon vanilla extract
  • ½ cup all-purpose flour
  • Pinch of salt
  • 1 cup quick oats

For the topping:

  • ¾ cup heavy whipping cream
  • 3 tablespoons powdered sugar


  1. For the peanut butter mousse: Chill a metal mixing bowl in the freezer for 5-10 minutes. Prepare the whipped cream. Pour 1 ¼ cups heavy whipping cream into the chilled bowl. Use an electric mixer to beat the heavy cream on medium-high speed until the cream starts to thicken. Slowly add the powdered sugar and continue beating on high speed until stiff peaks form. Set aside.
  2. In a medium-sized mixing bowl, combine the cream cheese and peanut butter and beat until well combined.
  3. Next add the sugar and vanilla extract and beat until well combined. Fold in the prepared whipped cream and mix until smooth. Refrigerate.
  4.  For the cookie dough: Soften the butter in the microwave for 10-15 seconds. Combined the softened butter with the sugars and mix until smooth.
  5. Add the peanut butter and vanilla extract and continuing mixing until well combined. Finally, add the flour, salt and quick oats and beat until a dough starts to form. Set aside.
  6. To assemble the dessert: Line the bottom of a 9-inch spring form pan with parchment paper. Assemble a layer of oatmeal cookies on the bottom, breaking apart the cookies as needed to fit.
  7. Divide both the mousse and the cookie dough into thirds. Spread 1/3 of the mousse over the bottom layers of oatmeal cookies. Crumble 1/3 of the cookie dough over the mousse and then sprinkle with a handful of MnMs. Repeat two more times. Save the top layer of cookie dough and MnM to add right before serving. Refrigerate for a minimum of 4 hours.
  8. For the topping: Prepare a second batch of whipped cream following the same instructions as listed above. Use a large open round tip to pipe the border of the cake. Sprinkle the top with remaining cookie dough and MnMs.


I suggest adding the final layer of cookie dough and MnMs to the top before serving. If the MnMs are cold or wet, the color will run.