Pre-heat the oven to 325°F (160°C) and line the bottom of 2 x 8-inch cake pans with parchment paper.
In a large bowl, whip the egg white with cream of tartar and a pinch of salt. Once the eggs become frothy, start adding in the sugar in a few stages. Mix until the sugar is fully dissolved, and the meringue reaches medium-stiff peaks.
Separately, in another bowl mix the egg yolks and vanilla until they become pale and frothy. Add in the warm milk and butter, mixing again to combine.
Sift in the cake flour and baking powder over the egg yolks. Add in ⅓ of the egg white meringue, then use a spatula to fold.
Once this initial meringue has been incorporated, add the rest of the meringue. Fold everything together with a spatula, without deflating the air in the meringue.
Divide the batter equally between the two pans, then rap the pans on the work surface to release any bubbles. Bake for 20-22 minutes or until a skewer comes out clean.
Once baked, let the cakes cool in the pans for 5-10 minutes, then remove and let them cool completely.
Whipped cream
Add the melted chocolate to a bowl, then pour warm heavy cream over it. Mix to combine.
Add the condensed milk and sugar into the chocolate mixture, then mix well to combine. Let the mixture cool down completely and chill for 1 hour.
Pour in ⅓ of the cold heavy cream into the chilled cream, then start whipping the mixture. Add in the remaining cream, mixing as you go along. Once the cream reaches stiff peaks, stop mixing.
Assembling the cake
Cut the strawberries into halves. Place them face down on a paper towel to remove any excess liquid.
If needed, trim the sponge cakes to level them. Place the bottom sponge cake on a cake stand, then cover it with a layer of whipped cream. Place the strawberry halves face down on the cream, then cover with more whipped cream.
Put the top vanilla sponge on top, without pressing down too hard.
Cover the cake with whipped cream, using a spatula to level it. If two layers are needed to cover the cake fully, chill the cake for 1 hour before applying the second layer.
Decorate with strawberry slices and more whipped cream.
Notes
I recommend using a kitchen scale in grams for more accuracy. The cups used for the conversion are standard US customary cups (1 cup flour = 136g). There are many different types of cups across the globe, which is why I strongly recommend using grams instead.
Flour - cake flour or type 000 flour yields a much softer cake. In this recipe cake flour cannot be replaced with all purpose flour.
Strawberries - you cannot replace fresh strawberries with frozen.
Storing - store in the fridge for up to 3 days. Decorate with fresh fruit before serving.