(THIS is supposed to be the authentic recipe)
Prinsesstårta (adapted from Vår kok bok)
For the sponge cake:
1 cup (225g) sugar
1/2 cup (62g) flour
1/2 cup (80g) potato starch flour
1 teaspoon baking powder
For the vanilla custard:
1 cup (240ml) heavy cream
4 egg yolks
3 tablespoons potato starch flour or 2 tablespoons corn starch
2 tablespoons sugar
4 teaspoons vanilla sugar or 2 teaspoons vanilla extract
For the assembly:
2 cups (480ml) heavy cream, whipped
10 ounces (300g) marzipan
green and yellow food coloring
powdered sugar for dusting
purchased marzipan rose and leaves for garnish or extra marzipan and red food coloring to make your own rose and leaves
Make the cake
1. Preheat the oven to 350°F (175°C). Thoroughly butter a 9″ x 2″ (2 liter) round baking pan. Toss in enough breadcrumbs to cover the bottom and sides of the pan and shake them around to ensure all surfaces are covered (the same as you would typically do with flour when baking a cake, you are just using breadcrumbs instead).
2. Place the eggs and sugar in a mixing bowl and beat on high speed until light colored and fluffy.
3. Blend the flour and baking powder together and carefully fold them into the egg and sugar mixture until thoroughly blended. Pour the batter into the prepared baking pan and bake in the lower portion of the oven for about 40 minutes or until golden and a toothpick comes out clean. Let the cake cool slightly in the pan before turning it out onto a rack to cool completely.
Make the vanilla custard
Place the cream, egg yolks, potato flour, and sugar in a small saucepan and whisk together (do not use a steel whisk as it can turn the custard grayish). Cook over low heat, stirring constantly, until the custard thickens. Remove from heat and stir in the vanilla. If cooking the custard with potato starch flour you need to use the custard shortly after you make it. If using corn starch the custard can be prepared a day ahead and stored in the refrigerator.
Prepare the marzipan
Knead the marzipan with your hands to soften it up and add the green and yellow food coloring sparingly until you have achieved a bright, spring green. Flatten the marzipan into a disk. Place it between two pieces of parchment paper or on a smooth surface dusted with powdered sugar and roll it into a thin, even circle ideally about 1/32″ (just under 2mm) thick but do the best you can to thin it out. Keep in mind the circle has to be large enough to cover the entire cake. You can dust the marzipan and work surface with powdered sugar if need be to prevent sticking.
Assemble the prinsesstårta (It’s helpful to refer to the pictures above)
Once the sponge cake has cooled completely, slice it into three layers keeping the top layer a bit thinner than the others. Start to assemble the prinsesstårta by spreading a thin layer of jam onto the bottom layer of the sponge cake. Add a generous layer of vanilla custard by either piping or spreading it over the jam. Add the next layer of sponge cake and another generous layer of vanilla custard. Whip the 2 cups (480ml) of heavy cream until stiff and pile a generous, fluffy mound onto the last custard layer. Add the final layer of sponge cake and gently form it into a dome shape over the cream being careful not to squish too much cream out of the sides. Spread a thin layer of cream over the top to even out and seal the surface. Gently lay the thin marzipan sheet over the top of the cake and use your hands to help define the shape. Trim the excess marzipan from the bottom of the cake by using a pizza or pastry wheel or a very sharp knife. Dust the top with sifted powdered sugar (you can use a tea strainer) and garnish with a pink marzipan rose with leaves. The cake needs to be refrigerated until serving time and any leftovers need to be refrigerated as well. Ideally the cake should be eaten the day it is made.