Norwegian Success Cake

Instructions

1. Prepare the cake pan
   Preheat oven to 325°F (165°C). Line the bottom and sides of a 9-inch (23cm) springform pan with parchment paper and lightly grease the paper.
2. Make the meringue base
   In a large, clean mixing bowl, beat the egg whites with cream of tartar until foamy. Gradually add 200g of sugar, beating continuously until stiff, glossy peaks form. Gently fold in the ground almonds and vanilla extract with a rubber spatula, being careful not to deflate the meringue too much.
3. Bake the meringue
   Spread the meringue mixture evenly in the prepared pan. Bake for 40-45 minutes, or until the top is golden and feels firm to the touch. Remove from oven and let cool completely in the pan.
4. Prepare the custard filling
   In a heatproof bowl, whisk together egg yolks and remaining 100g sugar until pale and creamy. In a saucepan, heat the cream just until it begins to simmer. Slowly pour the hot cream into the egg mixture, whisking continuously. Return the mixture to the saucepan and cook over low heat, stirring constantly, until it thickens enough to coat the back of a spoon, about 8-10 minutes.
5. Complete the filling
   Remove the custard from heat and stir in the salt. Let cool for 5 minutes, then gradually add the butter, a few cubes at a time, whisking until smooth and incorporated. If using, stir in the rum. Cool the filling to room temperature, then refrigerate for 30 minutes until it begins to set but is still spreadable.
6. Assemble the cake
   Once the meringue base is completely cool, carefully remove it from the springform pan. Spread the custard filling evenly over the top. Sprinkle with sliced almonds.
7. Chill and serve
   Refrigerate the cake for at least 2 hours, preferably overnight, to allow the flavors to meld and the filling to set properly. Before serving, let the cake sit at room temperature for 20-30 minutes for the best flavor and texture.