01 -
Preheat oven to 175°C. Grease and line a 23×33 cm baking pan with parchment paper.
02 -
Cream butter with granulated sugar until light and fluffy. Add oil, egg whites, and vanilla extract, beating well after each addition.
03 -
Incorporate flour, baking powder, baking soda, and salt. Alternate additions of dry ingredients and buttermilk, starting and ending with the dry mix. Mix just until combined.
04 -
Transfer batter evenly into prepared pan. Bake for 25–30 minutes or until a toothpick inserted in the center comes out clean. Allow cake to cool completely in the pan.
05 -
Mix milk with vanilla extract in a small bowl and set aside for assembly.
06 -
Beat butter until fluffy. Add cream cheese and mix until smooth. Gradually incorporate powdered sugar, beating after each addition, then add clear vanilla extract.
07 -
Combine flour, granulated sugar, brown sugar, baking powder, salt, oil, clear vanilla extract, and rainbow sprinkles in a bowl. Blend with a fork until clusters form. Spread on a lined baking tray and bake at 175°C for 20 minutes. Let cool completely.
08 -
Cut cooled cake horizontally into two layers. Place the bottom sheet on a serving platter. Brush with half the milk soak.
09 -
Spread a generous layer of frosting over the bottom cake sheet.
10 -
Place second cake layer on top. Brush with remaining milk soak and frost top and sides evenly.
11 -
Scatter baked crumbs liberally over the frosted cake surface.
12 -
Allow assembled cake to rest for at least one hour before slicing for optimal flavor and texture.