1-Make the caramel base: Melt brown sugar over lowest heat, then whisk in hot heavy cream until smooth.

2-Finish the caramel cream: Cool caramel to room temperature, whisk in cold heavy cream, salt, and vanilla, then refrigerate at least 4 hours.

3-Start the meringue: Whisk egg whites with cream of tartar until foamy, gradually add brown sugar, and beat on medium speed until glossy stiff peaks form.

4-Make the yolk batter: Whisk egg yolks with milk, oil, and vanilla, then sift in cake flour, cornstarch, baking powder, and salt; stir until smooth.

5-Fold the batter: Gently fold meringue into the yolk batter in 2–3 additions using a J motion until just combined.

6-Bake the cake layers: Divide batter between two parchment‑lined 8‑inch pans, place in a water bath, and bake at 325°F for 20–22 minutes; cool completely in pans.

7-Make the ganache and syrup: Stir warm heavy cream into milk caramel chocolate until smooth; simmer equal parts brown sugar and water until dissolved, then cool.

8-Whip the caramel cream: Once fully chilled, whip the caramel cream with an electric mixer on medium speed until thick, spreadable, and holding stiff peaks.

9-Assemble the cake: Split cakes into four thin layers, brush each with brown sugar syrup, spread caramel whipped cream, add a well of ganache between layers, and refrigerate at least 1 hour before slicing.