Put the milk in a saucepan on the stove, add the butter and heat until the butter dissolves. Remove from heat.

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

In a deep bowl, whisk the eggs with the sugar until fluffy and the sugar has fully dissolved.

Add the flour mixture and the milk mixture to the egg mixture in three additions, whisking each time. The batter is ready.

Pour the batter into the pan and bake in an oven preheated to 180 °C for 40 minutes. Let the sponge cool - it can stay right in the pan.

For the soak, whisk the sour cream with the condensed milk using a mixer.

Poke the sponge in several places with a skewer and pour the soak over it. Leave on the counter for a couple of hours, then refrigerate - ideally overnight, or at least a couple more hours. The soak should be fully absorbed, like a sponge.

Transfer the cake to a plate and decorate as you like - I used whipped cream and cocoa through a stencil. Bon appetit!