Ingredients
Equipment
Method
Bake the oatmeal cake layers
- Preheat oven to 350F, then grease two 9-inch round pans. Set the pans aside so they’re ready for batter.
- Beat butter and brown sugar until combined. Add eggs, then beat in sour cream and vanilla until smooth.
- Fold in flour, rolled oats, baking powder, baking soda, cinnamon, nutmeg, and salt. Mix just until no dry streaks remain.
- Divide batter evenly between the two pans. Bake for 30-35 minutes at 350F, until the centers spring back lightly.
- Cool cakes completely in the pans, then remove as needed. Let them cool fully so the filling won’t melt.
Make the marshmallow cream filling and assemble
- Beat softened unsalted butter and softened cream cheese until smooth. Add marshmallow creme and beat until incorporated.
- Beat in powdered sugar until the mixture becomes thick and fluffy. Add vanilla and continue beating until very fluffy with a spreadable texture.
- Frost between the cooled layers with the marshmallow cream. Spread a thick layer so it holds the cake together.
- Frost the outside of the cake with the remaining filling. Smooth the sides and top for a clean finish.
Notes
For the cleanest layers, cool the cakes fully before assembling; warm cake will cause the marshmallow cream to soften and slide. Store covered in the refrigerator up to 4 days. Freeze the baked (unfrosted) layers up to 2 months; thaw overnight in the fridge, then make and add filling. For a lighter option, use reduced-fat cream cheese in the filling (texture will be slightly less dense).