Preheat oven to 180C. Grease a baking dish (24cm in diameter). Line base and sides with baking paper.
Separate the yolks from the egg whites.
In a bowl, cream the butter at room temperature and half the sugar.
Then, add 2 egg yolks and mix them very well. Add the vanilla and yogurt.
Sift the yeast and add it to the mixture.
In another bowl, with an electric mixer, beat the remaining 2 egg whites until they are white and foamy. Then slowly add the remaining sugar and whip to firm peaks.
Using a large metal spoon, gently fold half the egg whites into butter mixture. Repeat with remaining egg whites.
Pour into prepared pan and bake at 180C for about 45-50 min. Test with a skewer to confirm that it is cooked.
Milk Chocolate Ganache filling: Pour the cream into a saucepan and cook over low heat. As soon as it starts to boil, remove from heat and add the chocolate and melt it. The mixture should be smooth and consistent. Let cool.
With a small stick of chocolate sugar paste, cut out the shape of a little sapling and star.
With gold powdered food coloring, coat the sugar star and let it harden in the open for about an hour.
Cut the cake in half. Using a spatula spread the inside with the milk chocolate ganache. Next, arrange the Ferrero Rocher in two rows along the edges of the cake.
Finally, insert a toothpick halfway up the sapling and star and then attach it to the top of the cake.