Start by preheating your oven to 350°F (175°C). Grease and flour your cake pans or line them with parchment paper for easy removal.

In a large bowl, combine the cake mix, whole milk, melted butter, egg yolks, and vanilla extract. Mix using a hand mixer or stand mixer on medium speed until the batter is smooth and well combined.

In a clean bowl, beat the egg whites with a pinch of salt until they form soft peaks. This step helps add air to the batter for a lighter cake.

Gently fold the whipped egg whites into the cake batter using a rubber spatula. Be careful not to deflate the mixture. This gives the cake a fluffy texture while keeping it moist and rich.

Divide the batter evenly between the prepared pans. Bake for 30 to 35 minutes or until a toothpick inserted in the center comes out clean. Let the cakes cool in the pans for about 10 minutes before transferring them to a wire rack to cool completely.

In a large bowl, beat the softened butter until creamy and smooth. Add in the dry pudding mix and French vanilla coffee creamer. Beat for another minute until incorporated. Gradually add the confectioner’s sugar, milk, vanilla extract, and salt. Beat on medium-high until the frosting is fluffy and smooth, about 3–5 minutes. Adjust the consistency by adding more milk if too thick or more sugar if too thin.

Once the cakes are fully cooled, spread a layer of buttercream on the first cake layer. Place the second layer on top and frost the top and sides evenly. Use an offset spatula for smooth application. Decorate as desired.