Preheat oven to 325F, generously grease the pan, sprinkle with flour and bang face down against the counter to release any access flour.

In a medium bowl, sift the flour, baking powder, and salt. Set aside.

Place the white chocolate in a medium bowl and melt in the microwave using 30-second increments until completely melted and smooth.

Do the same with the semi-sweet chocolate, set aside.

In a bowl of a standing mixer, mix on medium-high the butter and sugar until well combined about 2 minutes.

Add the eggs one and a time, waiting for each to completely incorporate before adding the next.

Scrape the bottom and sides of the bowl then add the flour mixture in three additions alternating with the milk starting and finishing with the flour mixture.

Right after adding the last portion of the flour, turn the mixer off then use a rubber spatula to incorporate the ingredients without over mixing the batter.

Dived the batter into two and fold in the white and semi-sweet chocolate in each part.

Dollop half of the white chocolate batter into the greased pan smooth into an even layer then do the same with half of the semi-sweet batter ontop. Repeat with the remaining batters.

Baker for 40 minutes or until a toothpick comes out clean (or with some crumbs) from the center of the cake.

Remove from oven and allow 10-15 minutes for the cake to cool before removing it from the pan.