Preheat oven to 180°C / 350°F. Line a 9×13 in (23×33 cm) pan with parchment paper.
Beat eggs and sugar until pale and fluffy.
Slowly add oil while mixing.
Sift flour, cocoa powder, baking powder, and salt. Gently fold into egg mixture.
Spread batter evenly into prepared pan and bake 15–18 minutes until a toothpick comes out clean.
Cool completely, then slice into two equal layers.
2. Make the Chocolate Custard
In a saucepan, whisk together sugar, cocoa powder, and cornstarch.
Gradually add milk while whisking to prevent lumps.
Cook over medium heat, stirring constantly, until thickened and bubbling.
Remove from heat, whisk in egg yolks (temper them first with a bit of hot custard), then return to heat for 1 minute.
Remove from heat again, stir in chocolate, vanilla, and butter until smooth.
Cover with plastic wrap touching the surface to prevent a skin from forming. Cool slightly (custard should still be pourable).
3. Assemble the Cake
Place one cake layer on a serving tray.
Spread warm chocolate custard evenly over it.
Place second cake layer on top and gently press.
Chill for at least 2 hours until set.
4. Add the Glaze
Melt chocolate and butter (or cream) together until smooth.
Pour glaze over chilled cake, spreading evenly.
Chill again until glaze is firm.
🍴 Serving
Cut into squares or slices with a hot knife (wiped clean between cuts). Serve chilled or at room temperature.
💡 Tips
You can soak the cake layers lightly with sweetened milk or rum syrup for extra moisture.
For a festive look, sprinkle chopped hazelnuts or walnuts over the glaze before it sets.
Best made a day ahead so the flavors blend beautifully.
Would you like me to include a vanilla-and-chocolate layered version (like Hungarian Diplomatakrémes) with alternating custard flavors for a more elegant presentation? 🇭🇺✨
