1c. unsalted butter, at room temperature, plus more for the pan
31/2c. all-purpose flour, plus more for the pan
21/2tsp. baking powder
1/2tsp. baking soda
1/2tsp. kosher salt
4oz. white chocolate, chopped
1/2c. just-boiled water
11/2c. granulated sugar
6 large egg whites
1tsp. pure vanilla extract
11/2c. buttermilk, at room temp
3oz. white chocolate, chopped
1/2c. unsalted butter (1 stick)
8oz. cream cheese, at room temperature (1 package)
1c. confectioners’ sugar
1/2c. heavy cream, cold
ASSEMBLY AND DECORATION
1/2c. seedless raspberry jam
royal icing snowflake transfers (see directions below)
white sugar flowers
confectioners’ sugar, for dusting
Make cake: Heat oven to 300°F. Butter and flour an angel food cake pan; tap out excess flour. In a large bowl, sift together flour, baking powder, baking soda, and salt.
Place white chocolate in a bowl, pour just-boiled water over the top, and stir until melted and smooth.
Using an electric mixer, beat butter and granulated sugar on medium-high speed until light and fluffy, 3 to 4 minutes.
Reduce mixer speed to medium and add egg whites 1 at a time, beating until each is fully incorporated, then beat in vanilla extract. Reduce mixer speed to low and add flour mixture in 3 parts, alternating with buttermilk and mixing just until incorporated. Mix in white chocolate mixture.
Spoon batter into prepared pan and bake until a wooden pick inserted into the center comes out clean, 75 to 80 minutes. Transfer cake to a wire rack and let cool 10 minutes before inverting onto wire rack to cool completely.
Make frosting: Microwave chocolate on 50% power in 30-second increments, stirring in between, until melted and smooth.
Using an electric mixer on low speed, beat butter and cream cheese until smooth. Add confectioners’ sugar and mix to combine, then mix in melted chocolate. Cover with plastic wrap and refrigerate until ready to use. Once ready to use, beat heavy cream until stiff peaks form. Stir a spoonful into cream cheese mixture, then fold in remaining whipped cream.
To assemble: To assemble, cut cake in half through equator. Transfer bottom half to serving platter and spread with jam and 3/4 cup cream cheese frosting; sandwich with top half. Cover cake with remaining cream cheese frosting and top with raspberries, sugar flowers, and snowflake transfers, then dust with confectioners’ sugar if desired.
Royal icing snowflake transfers: Print or draw a 1- to 2-in. snowflake design and place under a piece of waxed paper or parchment paper. Transfer royal icing to piping bag fitted with size 2 tip and use stencil as a guide to pipe snowflakes on top. Let dry completely, then use a small offset spatula to carefully remove.