Take out the ingredients from the refrigerator at least two hours in advance so they warm up properly - butter, eggs, buttermilk.

Line the baking pan with parchment paper or grease it with butter and dust with flour or breadcrumbs.

Mix together the flour, baking powder, and salt.

Turn on the oven to top/bottom heating at 180℃ or convection at 170℃.

Transfer butter, sugar, and vanilla to a mixer bowl. Beat them together on high speed for several minutes until you get a very light and fluffy mixture.

Add one egg at a time and one tablespoon of mixed flour to the butter mixture, then briefly mix on low speed.

Add about half of the remaining flour and mix briefly - just until combined.

Add buttermilk and mix briefly.

Pour in the rest of the flour and mix briefly - stop mixing when you can still see traces of flour on the sides of the bowl.

Then, just stir the dough with a spoon.

Transfer the dough to the prepared pan and bake for about 40-45 minutes - until a skewer comes out clean.

After baking, let the cake cool.

Transfer egg yolks, sugar, vanilla, and potato starch to a bowl and combine into a smooth mixture.

Heat the milk until hot, then gradually pour a portion of the milk into the mixed egg yolks, continuously stirring the mixture.

Pour the egg yolks with milk back into the saucepan and bring to a boil - cook, stirring constantly, until you get a thick pudding.

Then remove it from the heat, add cold butter, and mix until combined.

Cover the surface of the pudding with plastic wrap, ensuring it touches the pudding, and set aside the cream to cool completely.

Mix together the ingredients for soaking the cake.

Gently trim the top of the cake, then make dense holes all over the cake.

Slowly pour the soaking liquid over the cake until it's all used up.

Spread the pudding cream over the cake.

Before serving, cut the cake into portions. Sprinkle each piece with granulated sugar on top.

Using a culinary torch, caramelize the sugar on top of the cake.

Serve the cake immediately - enjoy!