Whip the cream by pouring cold heavy whipping cream into a mixing bowl and whip on medium speed until soft peaks form. Add icing sugar gradually and whip until stiff peaks and fluffy.

Warm creamy peanut butter in the microwave for 15-20 seconds until pourable. Fold it into the whipped cream until fully combined.

Prepare a 9x5 loaf pan by lining it with cling wrap or parchment paper, extending edges for easy removal.

Dip oatmeal cookies quickly into whole milk to moisten. Lay them in a single layer at the bottom of the pan.

Spread one-third of the peanut butter whipped cream mixture over the first layer of cookies. Sprinkle with mini chocolate chips and mini M&Ms.

Repeat the layering process two more times, using remaining ingredients. Finish with a layer of whipped cream on top.

Cover the cake with plastic wrap and refrigerate for at least 4 hours to set or freeze for 2 hours for a firmer texture.

Remove the cake from the pan using overhanging wrap. If frozen, let it sit for 5 minutes for easier slicing. Cut and serve chilled.