Add the frozen raspberries to a medium saucepan over medium heat. Cook for about 10 minutes, stirring and mashing occasionally, until the raspberries begin to break down and are liquidy.

Pass the raspberries through a sieve to remove the seeds. You should have just under 2 cups (480 ml) of liquid.

Return the raspberry liquid to the saucepan, off the heat, and whisk in the cornstarch and sugar.

Heat the mixture over medium heat for about 25 minutes until the jam is thick. It should measure out to 1 ½ cups (360 ml).

Transfer the jam to a small bowl. Let the jam chill while working on the rest of the cake.

Preheat the oven to 350℉ (175 ℃). Grease a 9×9in pan and line it with parchment paper.

In a medium bowl, whisk together the cake flour, baking powder, baking soda, and salt. Then set aside the flour mixture.

Add the softened butter and granulated white sugar to a large bowl. Cream together for 2 minutes with an electric mixer.

Then add in the egg whites and vanilla and mix on medium speed until pale in color and smooth, about 1 minute.

Add the dry ingredients and buttermilk to the wet ingredients a little at a time, mixing on low speed until the cake batter is combined. Scrape the sides of the bowl with a rubber spatula as necessary.

Pour the batter into the prepared pan. Bake the cake for 35-40 minutes or until a toothpick comes out clean from the center.

Let the cake cool in the pan on a wire rack for 30 minutes. Carefully pull up on the parchment paper to release the cake from the pan, then continue to cool it on the wire rack until completely cooled.

In a liquid measuring cup, whisk the half & half, sweetened condensed milk and vanilla together. Chill in the fridge until ready to use.

Add the butter to a large mixing bowl and mix on high speed with an electric mixer until pale and fluffy, about 5 minutes.

Then add in the cream cheese and mix on high speed until fluffy, about 1 minute.

Add in the melted and slightly cooled white chocolate. Mix on medium speed until combined.

Add in ¼ cup of the raspberry jam and mix on medium speed until combined.

Sift in the powdered sugar. Mix on low speed until combined, then on high speed for 1 minute until fluffy.

When the cake is completely cooled, cut a very thin layer off the top of the cake off using a sharp knife.

Transfer it to a serving plate. Poke holes on the top of the cake using a wooden stick or the handle of a wooden spoon.

Slowly pour the vanilla milk mixture on top of the cake.

Reserve 2 tablespoon of jam, then add the remaining portion jam to a piping bag. Pipe the jam into the holes of the cake.

Frost the top of the cake with a thick layer of white chocolate raspberry cream cheese frosting using an offset spatula.

Swirl the remaining bit of jam into the frosting using the back of a spoon. Then cut into 16 slices and serve!