Start by soaking the rolled oats in a bowl with the milk, molasses, and vegetable oil. Let this mixture sit for about 15 minutes.

While the oats soak, preheat your oven to 350°F (175°C) and prepare two 8-inch round cake pans.

In a large mixing bowl, whisk together the all-purpose flour, baking powder, baking soda, ground cinnamon, and salt.

Cream the softened unsalted butter with both the granulated and light brown sugars until light and fluffy, about 3-5 minutes.

Add the large eggs to the creamed mixture one at a time, mixing well after each addition until there are no streaks of egg visible.

Slowly add the dry flour mixture and the soaked oats into the wet ingredients, alternating them to maintain a smooth batter.

Place the filled cake pans into the preheated oven and bake for 30-35 minutes, or until a cake tester comes out clean.

After 10 minutes, carefully transfer the cakes to a wire rack to cool completely.

In a mixing bowl, whip the softened butter until airy and fluffy, then mix in the confectioners sugar and heavy whipping cream.

Combine a portion of the prepared frosting with the marshmallow cream in a separate bowl, adding more confectioners sugar to achieve the right consistency.

Level the cooled cake layers if necessary, and slice each layer in half for a total of four layers. Begin assembly by placing the first layer on a serving platter, and repeat layering of marshmallow filling and frosting.

Apply a crumb coat to seal everything in before chilling the cake for about 30 minutes, then finish frosting and garnish with crumbled oatmeal cream pies.