Preheat oven to 350 degrees Fahrenheit. Lightly grease your heart shaped cake pans or molds and set aside.
In the bowl of a standing mixer, beat together the sugar and butter until they are light and fluffy. Add in the egg whites and vanilla and beat for another minute.
Whisk together the cake flour, salt, baking powder, and baking soda. Add the flour mixture to the butter mixture in the bowl of the standing mixer, along with the yogurt. Mix for another 2 to 3 minutes, scraping the sides as needed, until the mixture is creamy and smooth. Note: if the mixture is too thick, add 1 to 2 tablespoons of milk until it resembles a thick but creamy batter.
Gently fold in the melted white chocolate.
Spoon the batter into the 4-inch cake pans, filling them only 2/3 full. If you fill them too full, the cakes will sink in the middle. (I put a scant 1/2 cup batter into each pan).
Bake for 20 to 25 minutes or until the top of the cake is beginning to turn golden. Remove from oven and let sit for 5 minutes before turning out onto a wire rack to cool completely.
While the cakes are cooling, mix up the White Chocolate Raspberry Cream. In a large bowl, whip the cream plus one heaping tablespoon of powdered sugar using an electric hand mixer until stiff peaks form. Fold in the jam and melted white chocolate.
Cut out of the center of the cooled cakes, leaving the bottom intact. I used a heart shaped cookie cutter, but you can easily eye it. Discard (or snack on!) the cake crumbs you remove.
Fill the center of each cake with the cream filling, then top generously with fresh raspberries and a dusting of powdered sugar. Serve immediately.