Preheat your oven to 350°F (175°C) and prepare two heart-shaped pans by greasing and flouring them.

In a medium bowl, whisk together the dry ingredients: flour, cornstarch, baking powder, baking soda, and salt.

In a large mixing bowl, beat the softened butter until creamy. Gradually add sugar and beat until light and fluffy.

In another bowl, whisk together the milk and sour cream until smooth for a creamy batter.

Gradually combine the dry ingredients with the wet ingredients, mixing on low speed until just combined.

Reserve 2 cups of the plain batter, then divide the remaining batter into three bowls and tint with food coloring.

Pour half of the reserved plain batter into a lined 9×13 inch pan and pipe blobs of colored batter on top before baking.

In the heart-shaped pans, dollop the batters randomly and swirl them to create a playful pattern.

Bake the cakes at 350°F, checking for doneness after 25-32 minutes.

Cool the cakes in the pans for 10-15 minutes before transferring to a wire rack.

Trim the tops of the cooled cakes for even stacking and chill layers for 20-30 minutes.

For the buttercream, beat the butter until smooth, gradually adding powdered sugar and cream until fluffy.

Reserve some buttercream for filling, then tint the rest in the desired colors.

Assemble the cake on a board with a layer of buttercream, stacking the layers and applying a crumb coat.

Spread a base coat of frosting over the entire cake, smoothing it out evenly.

Decorate with piped spots of brown and outlines of black buttercream for a whimsical finish.

Chill the cake before slicing to ensure clean edges when serving.