Melt the butter in a saucepan over low heat. Once melted, add the milk, water, and salt. Bring to a gentle boil.

In a separate bowl, mix the flour and baking powder together.

Gradually add the flour mixture to the saucepan, stirring constantly until you have a smooth dough.

Preheat the oven to 200 degrees Celsius (around 400 degrees Fahrenheit).

Once the dough has cooled slightly, add the eggs one at a time, mixing thoroughly after each addition.

Line a 25 cm round cake tin with parchment paper and pour half of your batter into the prepared tin.

Bake in the preheated oven for about 20 minutes, or until golden brown.

Repeat the process with the remaining batter to bake the second crust.

In a bowl, beat the eggs and sugar until well mixed then gradually add the flour, stirring to ensure no lumps.

In another saucepan, heat the milk again and slowly add the egg mixture, stirring continuously until thickened.

Let the creamy filling cool before mixing with whipped butter until smooth and creamy.

Spread the creamy filling over one of the cooled cake layers and place the second layer on top.

Refrigerate the assembled cake for about 2 hours.

After chilling, slice the cake and serve, optionally dusting with powdered sugar.