Let egg whites sit at room temperature for 30 minutes in a mixing bowl.

Grease and flour two round baking or cake pans then put aside.

Stir the flour, baking powder, and salt together before setting aside dry ingredient mixture.

Melt chopped up white baking bar in saucepan with 1/4 cup of half-and-half over low heat. Stir continuously but slowly to allow bar to melt.

Remove from heat and keep stirring until the bar is melted and smooth. Add in remaining half-and-half and let white chocolate mixture cool.

In a large bowl, beat the butter with an electric mixer or stand mixer on medium to high speed for around 30 seconds.

Add sugar and vanilla and beat until they are combined, then slowly add each egg yolk.

Add dry flour mixture and the white baking bar mix, beating the entire concoction on low speed to medium speed.

Clean off beaters, then beat egg whites with your mixer on high speed until you see stiff peaks. Add egg whites into batter, then spread it in the prepared pans.

Bake the white chocolate cakes at 350 degrees Fahrenheit for about half an hour, or until a toothpick comes out clean.

Let cake cool on wire racks for around 10 minutes, then remove from the pans and let cool even more before frosting and serving.