Preparation

• Make & cool the raspberry sauce. First prepare the raspberry filling according to the recipe here. Allow the raspberry sauce to cool completely and chill for at least 30 minutes before using. Cover and store for up to 1 week in the refrigerator.
• Preheat oven to 350°F. Line the base of two 8-inch round cake pans and line the base with rounds of parchment paper.
• Make the cake batter. Sift flour, baking powder, baking soda and salt into a medium bowl and whisk to blend evenly.
• Combine soft butter, oil, sugar and vanilla in a large bowl and beat with an electric hand mixer for 2 minutes until pale and fluffy. Beat in egg until well incorporated. Add egg whites and beat until well combined and smooth. Mix in sour cream. Sift in half of the flour over the wet mixture and mix it in slowly. Gradually beat in half of the milk. Mix in remaining flour and then rest of the milk. Beat on high for the last 5 seconds to emulsify the batter. Gently fold in raspberries.
• Divide the batter evenly between the prepared pans and bake for 25-30 minutes until lightly golden and a skewer inserted into the center comes out clean. Transfer pans to a wire rack and let cool for 20-30 minutes in the pan, then run an offset spatula or knife around the edges to loosen them, invert, remove the bottom layer of parchment and let completely on the racks.
• Make the frosting. Place chopped white chocolate into a large bowl. Pour ½ cup of cream into a saucepan with the scraped vanilla bean seeds and place over medium heat. Watch it as it comes to a simmer. Once simmering, immediately pour it over the chopped chocolate, cover the bowl and let stand for 2 minutes. Uncover the bowl and whisk until the chocolate is completely melted and the mixture is smooth and silky. Let it cool for 5 minutes so it is no longer hot, and then whisk in remaining cold cream. Place the bowl in the fridge and chill for at least 2 hours or overnight until completely cold.
• Once thoroughly chilled, add the vanilla extract and beat with an electric hand mixer on medium speed until thick and fluffy.
• Assemble the cake. Place one cake layer on a serving plate. Fill a piping bag with about 1 cup of frosting and pipe around the circumference of the cake to build a wall that will keep the filling from squeezing out. Spread 1 cup of raspberry filling over the top of the cake within the frosting border. Place the other layer on top so it aligns with the sides of the bottom layer. Cover the entire cake with frosting and use a large offset spatula to even out the sides and make swooshes and swirls on the top layer. Decorate with fresh raspberries.