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Giant Oatmeal Cream Pie Cake | Easy Nostalgic Dessert
Stephanie Moore

Giant Oatmeal Cream Pie Cake

Indulge in a nostalgic treat reimagined as a show-stopping cake. This recipe features two layers of moist, spiced oatmeal cake enriched with molasses and brown sugar, sandwiching a fluffy, cloud-like marshmallow cream filling. Perfect for gatherings, this giant version of the classic childhood cookie offers the perfect balance of chewy texture and decadent sweetness. It is the ultimate dessert for those who appreciate a sophisticated, homemade touch on a retro favorite.
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Prep Time 25 minutes
Cook Time 30 minutes
Total Time 55 minutes
Servings: 12 servings
Course: Desserts
Cuisine: American
Calories: 420
Ingredients Method Notes

Ingredients
  

  • 1.5 cups old-fashioned rolled oats
  • 1.5 cups boiling water
  • 1 cup unsalted butter, melted
  • 1 cup granulated sugar
  • 1 cup brown sugar, packed
  • 2 large eggs
  • 1 tablespoon vanilla extract
  • 2 tablespoons molasses
  • 2 cups all-purpose flour
  • 1 teaspoon baking soda
  • 1 teaspoon ground cinnamon
  • 0.5 teaspoon salt
  • 1 cup unsalted butter, room temperature (for filling)
  • 2 cups confectioners' sugar
  • 7 ounces marshmallow fluff

Method
 

  1. Preheat your oven to 350°F (175°C) and grease two 9-inch round cake pans.
  2. Combine the rolled oats and boiling water in a bowl and let sit for 15 minutes.
  3. Cream together the melted butter, granulated sugar, and brown sugar in a large bowl.
  4. Beat in the eggs one at a time, then mix in the vanilla and molasses.
  5. In a separate bowl, whisk together flour, baking soda, cinnamon, and salt.
  6. Gradually fold the dry ingredients into the butter mixture, alternating with the oat mixture.
  7. Divide the batter into the prepared pans and bake for 25-30 minutes, or until a toothpick comes out clean.
  8. Allow the cakes to cool completely on a wire rack.
  9. For the filling, beat the room-temperature butter until pale and fluffy using a stand mixer.
  10. Gradually beat in the confectioners' sugar until smooth.
  11. Fold in the marshmallow fluff until well combined.
  12. Assemble by spreading the filling between the two cooled cake layers.

Notes

Ensure the cake layers are completely cold before frosting to prevent the marshmallow filling from melting. Store the cake in an airtight container at room temperature for up to three days.