Instructions
Cake
Step 1
Preheat the oven to 350 F/180 C. Line three 8-inch cake pans with parchment paper on the bottoms and set them aside.
Step 2
Bring a pot of water to a boil. Add in the oats, stir, and remove the pot from the heat. Cover the pot for 20 minutes. Let the oatmeal cool to room temperature before using.
Step 3
Whisk together the flour, baking soda, salt, cinnamon, and nutmeg and set aside.
Step 4
In a stand mixer, beat the butter and sugars together on medium speed for 5 minutes until light and fluffy. Add in the vanilla, eggs, and sour cream and mix until combined, scraping the sides of the bowl as necessary.
Step 5
Mix in the cooked oats and mix until just combined. Then fold in the flour mixture, mixing until just combined. It will be a very thick batter!
Step 6
Spread batter into pans (around 600g each). Bake for 20-22 mins, until a toothpick comes out covered in a few moist crumbs. Cool in pans on a wire rack, then run a spatula around the edges to flip them out.
Vanilla Cream Buttercream
Step 1
Whisk egg whites and sugar in a stand mixing bowl. Place over a double boiler, whisking occasionally, until a thermometer reads 165°F and the sugar fully dissolves, about 9-11 minutes.
Step 2
Fit the bowl to the stand mixer with the whisk attachment. On medium-high speed, beat the mixture until stiff glossy peaks form and the meringue is no longer warm to the touch, at least 10-15 minutes.
Step 3
Add the butter 1 tablespoon at a time, waiting until the butter has fully combined before adding the next. Then turn the mixer down to medium speed and mix in the vanilla bean paste and salt.
Vanilla Glaze
Step 1
Heat cream on the stove or microwave, then pour over the white chocolate chips, stirring to combine. Add the white food coloring for a less yellow tone (optional). Let it cool before pouring it over the cake to avoid melting the frosting.
Assembly
Step 1
Assemble by placing an oatmeal cake layer on a stand. Spread 1 cup of vanilla frosting on top. Add the next layer. Alternate cake and frosting layers, finishing with the top layer upside down for a flat surface.
Step 2
Spread the rest of the frosting across the sides and top of the cake in a thin, even layer.
Step 3
Put the cake on a wire rack with a pan below. Pour the glaze in the center, spreading it to the edges so it falls off the sides. Let the glaze finish running off and set. Then decorate the top of the cake with crumbled oatmeal pie cookie crumbs and pieces.
