Place the first 6 oz of white chocolate into a bowl. Microwave on high for 1 minute, stir. Microwave for one more minute, and stir again until completely melted. Let it cool for a few minutes.
Combine the cake mix, eggs, lemon juice, water and oil. Mix well for several minutes. Whisk in the melted white chocolate.
Grease and flour 2 round 8-inch cake pans. Add the batter. Bake for 28-32 minutes at 350 degrees, or until golden brown/fragrant and a toothpick comes out clean.
Allow the cakes to cool in the pans for about 10 minutes. Then turn out onto a wire rack and let cool completely.
For the frosting: Melt the remaining 6 oz chocolate chips as in step 1.
Cream the butter and neufchatel cheese together until fluffy. Slowly add the powdered sugar (NOTE: make sure it is well sifted, or there will be lumps!) and mix well until combined.
Whisk in the white chocolate, the pinch of salt and the lemon juice. Check the consistency, beat in more butter or powdered sugar if needed. Note: the frosting will solidify slightly once refrigerated.
Evenly spread the top of one of the cooled cakes with the raspberry jam.
Place the second cake on top. Using a spatula or frosting knife, spread the frosting evenly over the top and sides of the cake. Decorate with leftover frosting, if desired.
Garnish with the fresh raspberries, and keep refrigerated.