Step 1

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.

Step 2

In a medium-sized mixing bowl, combine the cream cheese and peanut butter and beat until well combined.

Step 3

Next add the sugar and vanilla extract and beat until well combined. Fold in the prepared whipped cream and mix until smooth. Refrigerate.

Step 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.

Step 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.

Step 6

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.

Step 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.

Step 8

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.