In a saucepan over low heat, melt the brown sugar until it becomes a smooth syrup. Slowly whisk in 1 cup warm heavy cream. Let cool, then stir in 2 cups cold cream, vanilla, and salt. Chill the mixture for at least 90 minutes.
Separate eggs into two bowls. Whip the whites with ¼ cup brown sugar until stiff peaks form. In a separate bowl, whisk yolks with the remaining sugar, milk, oil, and vanilla. Sift in flour, cornstarch, baking powder, and salt, then mix.
Gently fold the meringue into the yolk mixture in batches until just combined. Divide the batter between two 8-inch pans lined with parchment paper.
Bake at 325°F for 20–22 minutes or until a toothpick comes out with a few crumbs. Cool completely in the pans.
Make the ganache by pouring hot cream over chopped chocolate. Let sit, then stir until smooth. Refrigerate until slightly thickened but pourable.
Whip the chilled caramel cream until stiff and spreadable.
Slice each cake horizontally to make 4 layers. Brush each with brown sugar syrup, then spread with caramel cream. Create a well in the center and fill with ganache. Repeat for all layers.
Frost the outside of the cake with the remaining caramel cream. Chill before serving for best results.
Notes
If caramel seizes, gently reheat and stir until smooth.
Use a kitchen scale for accurate measurements.
Make sure the cream is thoroughly chilled before whipping.
Fold the meringue gently to avoid deflating the batter.
This cake is best served chilled and can be made 1–2 days ahead.
