01 - Preheat your oven to 350°F (175°C). Prepare four 4-inch (10 cm) round cake pans or ramekins by greasing and lining them.
02 - In a mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and salt.
03 - In a separate bowl, combine the vegetable oil, whole milk, large egg, and vanilla extract.
04 - Incorporate the wet ingredients into the dry ingredients and mix until just combined; avoid overmixing.
05 - Divide the prepared batter evenly among the four prepared pans.
06 - Bake for 20 to 25 minutes, or until a toothpick inserted into the center of the cakes comes out clean. Allow to cool completely.
07 - For the buttercream frosting, beat the softened unsalted butter until creamy. Gradually add the powdered sugar, mixing until combined. Incorporate the milk and vanilla extract, then beat until the frosting is light and fluffy. Divide the frosting into separate bowls and tint with gel food coloring as desired.
08 - Level the cooled cakes and apply a thin layer of frosting (crumb coat) to each, followed by a final decorative layer.
09 - Utilize the colored buttercream, edible markers, fondant shapes, sprinkles, sugar eyes, and mini candies to craft playful designs, such as funny faces, characters, emojis, or whimsical messages.
10 - Chill the decorated cakes for a minimum of 20 minutes before serving to ensure optimal texture and presentation.