Preheat the Oven: Set your oven to 325°F (163°C) to allow it time to heat up while you prepare the batter.
Cream Butter and Sugar: In a large bowl, cream softened butter with granulated sugar. Use an electric mixer on medium speed for 3-5 minutes, until the mixture is light and fluffy.
Add Eggs: Add eggs one at a time, mixing thoroughly after each addition to ensure a smooth batter.
Incorporate Melted Chocolate: Gently fold in room-temperature melted chocolate, aiming for a lighter batter color as intended in the recipe.
Mix in Leavening Agents: Add baking powder, baking soda, and salt to the mixture, blending well to create a light and airy texture in the cake.
Add Cornstarch, Flour, and Milk: Stir in cornstarch, then alternate adding all-purpose flour and evaporated milk to the mixture, beginning and ending with flour. Avoid overmixing to keep the batter tender.
Bake and Cool: Pour the batter into two greased 9-inch round cake pans and bake for 20-25 minutes, or until a toothpick comes out clean. Allow cakes to cool in pans for 5 minutes, then transfer to a wire rack to cool completely before frosting or serving.