Preheat your oven to 350°F (175°C) and grease your heart-shaped cake pans with softened butter, then flour them or line with parchment paper.
In a medium bowl, whisk together 2 ¾ cups of flour, 1 tablespoon of cornstarch, 2 ¼ teaspoons of baking powder, ½ teaspoon of baking soda, and ½ teaspoon of fine sea salt.
In a large bowl, beat 1 cup of softened unsalted butter until creamy. Gradually add 1 ¾ cups of granulated sugar and beat until light and fluffy (3-4 minutes).
Add 4 large eggs, one at a time, mixing well after each addition, then mix in 2 teaspoons of pure vanilla extract.
In a separate bowl, whisk together 1 ¼ cups of whole milk and ½ cup of sour cream. Gradually add the dry ingredients to the butter mixture, alternating with the milk mixture.
Reserve 2 cups of plain batter. Divide 1 cup of the remaining batter into three bowls and tint one golden yellow, another medium brown, and the last ½ cup black or very dark brown.
Pour half of the reserved plain batter into a lined 9×13 pan, pipe fun patterns with the brown and black batters, then cover with yellow batter. Bake for 12-16 minutes and cool before cutting heart shapes.
Fill your heart-shaped pans with a thin layer of plain batter, dollop colored batters, and swirl them together. Bake for 25-32 minutes if using 8-inch pans, or 40-50 minutes for one deep 9-inch pan.
Let the cakes cool in the pans for 10-15 minutes, then transfer to a wire rack to cool completely.
Level the cakes if domed, and chill them in the refrigerator for 20-30 minutes.
Beat together 1 ½ cups of softened unsalted butter until creamy, then gradually add 5-6 cups of sifted powdered sugar and alternate adding ¼ cup of heavy cream until desired frosting consistency is achieved.
Reserve 1 cup of ivory frosting for filling. Tint remaining frosting golden tan, divide again to tint portions brown and black for piping details.
Layer one cake on a serving plate with frosting for stability, spread filling, stack the second layer, and apply a crumb coat before chilling until firm.
Apply a smooth base coat with golden tan frosting over the entire cake, then chill again to set.
Pipe cheetah print spots in brown and black frosting on the cake, varying the spot sizes for a natural look.
Chill the decorated cake for 30-45 minutes, then slice with a warm knife to serve.