Vanilla Walnut Cake with Creamy Custard Filling

Servings: 8–10 slices
Steps to Make Vanilla Walnut Cake with Creamy Custard Filling
Step 1: Prepare the Cake Batter
Preheat the oven: Set your oven to 180°C (350°F) and grease a round or rectangular baking pan.
Beat the eggs and sugar: In a large mixing bowl, beat the eggs, sugar, and vanilla sugar until the mixture is pale and fluffy. This takes about 5 minutes with a hand or stand mixer.
Add the wet ingredients: Gradually mix in the milk and vegetable oil.
Combine the dry ingredients: In a separate bowl, sift together the flour, baking powder, and salt. Slowly fold the dry ingredients into the wet mixture, stirring until just combined.
Incorporate the walnuts: Gently fold in the chopped walnuts for a nutty texture.
Step 2: Bake the Cake
Pour the batter into the prepared baking pan and smooth the surface with a spatula.
Bake in the preheated oven for 30–35 minutes, or until a toothpick inserted into the center comes out clean.
Remove the cake from the oven and let it cool completely in the pan before transferring it to a wire rack.
Step 3: Prepare the Custard Filling
Heat the milk: In a medium saucepan, heat 700 ml of the milk over medium heat until it begins to simmer. Do not boil.
Mix the egg yolks and starch: In a separate bowl, whisk together the egg yolks, sugar, vanilla sugar, corn starch, and the remaining 100 ml of milk until smooth.
Combine and cook: Gradually pour the egg yolk mixture into the hot milk, whisking continuously to prevent lumps. Cook over medium heat, stirring constantly, until the mixture thickens into a smooth custard. This takes about 5–7 minutes.
Add the butter: Remove the custard from heat and stir in the butter until fully melted and incorporated.
Cool the custard: Transfer the custard to a bowl, cover with plastic wrap (pressing it directly onto the surface to prevent a skin from forming), and let it cool completely at room temperature.